آمانتدین
Amantadine Hydrochloride (Symmetrel)
آمانتدین

نام ژنریک

Amantadine HCl

شکل دارویی

اشكال دارويي:


Capsule: 100mg

موارد مصرف

موارد و مقدار مصرف


الف) پيشگيري يا درمان علامتي ناشي از ويروس آنفلوانزا تيپ A در بيماران ضعيف يا سالمند.


بزرگسالان (64-13 ساله) : مقدار 200 ميلي‌گرم يك بار، يا 100 ميلي‌گرم دو بار در روز مصرف مي‌شود.


بزرگسالان با سن بيش از 64 سال : مقدار 100 ميلي‌گرم يك بار در روز مصرف مي‌شود.


كودكان 12-9 ساله: مقدار mg 100، دو بار در روز مصرف مي‌شود. در كودكاني كه 10 سال يا بيشتر سن داشته باشند و وزن آنها بيش از kg 40 باشد، مي‌توان از دوز بزرگسالان استفاده نمود.


كودكان 9-1 ساله: مقدار mg/kg 8/8-4/4 در دو يا سه مقدار منقسم مصرف مي‌شود. جهت كاهش سميت، روزانه mg/kg 5 در يك يا دو دوز مصرف مي‌گردد. مقدار مصرف روزانه نبايد از 150 ميلي‌گرم تجاوز كند.


درمان بايد به مدت 48-24 ساعت بعد از از بين رفتن نشانه‌هاي بيماري ادامه يابد. پيشگيري بايد بلافاصله بعد از اولين برخورد با ويروس شروع شود و حداقل تا 10 روز ادامه يابد. در صورت عدم دسترسي به واكسن ويروس آنفلوآنزا يا تماس مكرر با اين ويروس، درمان پيشگيري ممكن است تا 90 روز ادامه يابد. در صورت استفاده از واكسن ويروس آنفلوآنزا، مصرف دارو 3-2 هفته ادامه مي‌يابد تا محافظت لازم از طريق واكسن به وجود آيد.


ب) درمان واكنش‌هاي اكستراپيراميدال ناشي از مصرف دارو.


بزرگسالان: مقدار 100 ميلي‌گرم دو بار در روز تا mg/day300 در مقادير منقسم مصرف مي‌گردد.


پ) درمان پارکينسونيسم ايديوپاتيك، سندرم پاركينسون.


بزرگسالان: در افراد به شدت بيمار، مقدار 100 ميلي‌گرم دو بار در روز تجويز مي‌شود. بيماراني كه از داروهاي ديگر ضد پاركينسون استفاده مي‌كنند ، مقدار mg/day100 به مدت حداقل يك هفته و سپس 100 ميلي‌گرم دو بار در روز، برحسب نياز، مصرف مي‌شود. بيمار ممكن است به mg/day400 نياز داشته باشد، ولي مصرف مقادير بيش از mg/day 200 را بايد به دقت تحت نظر قرار داد.


در بيماران مبتلا به اختلال عملکرد كليه كاهش مقدار مصرف دارو ضرورت دارد.


مقدار مصرف در نارسايي كليه


در بيماران مبتلا به نارسايي كليه، مقدار مصرف بر اساس كليرانس كرآتينين مشخص مي‌شود. بنابراين، اگر كليرانس كرآتينين 50-30 ميلي‌ليتر در دقيقه باشد، 200 ميلي‌گرم در روز اول و سپس mg100 روزانه، اگر 29-15 ميلي‌ليتر در دقيقه باشد، مقدار 200 ميلي‌گرم در روز اول و سپس 100 ميلي‌گرم يك روز در ميان و اگر كمتر از 15 ميلي‌ليتر در دقيقه باشد يا در بيماراني كه تحت همودياليز درازمدت قرار مي‌گيرند، مقدار 200 ميلي‌گرم هر هفته مصرف مي‌شود.


مكانيسم اثر


اثر ضد ويروس: آمانتادين با نفوذ ويروس آنفلوآنزا تيپ A به داخل سلول‌هاي مستعد تداخل مي‌كند كه اين كار را با مهار هماگلوتينين ويروسي انجام مي‌ دهند. در شرايط آزمايشگاهي ، آمانتادين فقط در مقابل ويروس آنفلوآنزا تيپ A فعال است (با اين وجود ، مقاومت خودبه‌خودي به طور شايعي اتفاق مي‌افتد). در محيط داخل بدن ، در 90-70 درصد موارد، آمانتادين ممكن است بدن را در مقابل ويروس آنفلوآنزا تيپ A حفظ كند. در صورتي كه اين دارو طي 48-24 ساعت پس از شروع بيماري مصرف شود ، طول مدت تب و ساير نشانه‌هاي سيستميك را كاهش مي‌دهد.


اثر ضد پاركينسونيسم: تصور مي‌شود آمانتادين باعث آزاد شدن دوپامين جسم سياه (substantia nigra) مي‌شود.

موارد منع مصرف

تداخل دارويي


مصرف همزمان با تري هگزي فنيديل و بنزتروپين (با مقادير مصرف بالاي اين داروها) عوارض جانبي آنتي‌كولينرژيك آنها را تشديد مي‌كند، كه اين امر احتمالاً باعث کانفوزيون و توهمات مي‌شود. در صورت بروز اين علائم ، دوز هر دو دارو بايد كاهش يابد.


مصرف همزمان با تركيب هيدروكلروتيازيد و تريامترن ممكن است دفع آمانتادين را كاهش دهد كه به افزايش غلظت سرمي آمانتادين و احتمالاً افزايش سميت دارو منجر مي‌شود. از مصرف همزمان آنها پرهيز گردد.


مصرف همزمان با محرك‌هاي CNS ممكن است سبب تحريك تجمعي شود.


مصرف همزمان با الكل ممكن است به منگي، کانفوزيون، غش و كمي فشارخون منجر شود.


ممكن است كوتريموكسازول كليرانس كليوي آمانتادين را كاهش داده و منجر به افزايش خطر دليريوم شود. از مصرف همزمان اين داروها پرهيز گردد.

موارد قابل توجه

-

تداخل دارویی

عوارض جانبي


اعصاب مرکزي : افسردگي، خستگي، کانفوزيون، سرگيجه، سايكوز، توهمات، اضطراب، تحريك‌پذيري، آتاكسي، بي‌خوابي، ضعف، سردرد، منگي، اشكال در تمركز حواس.


قلبي ـ عروقي: ادم محيطي ، كمي فشارخون در حالت ايستاده، نارسايي احتقاني قلب.


پوست: كبودي پوست (با مصرف دراز مدت).


دستگاه گوارش: بي‌اشتهايي، تهوع، يبوست، استفراغ، خشكي دهان.


ادراري ـ تناسلي: احتباس ادرار.


توجه: در صورت بروز واكنش حساسيت مفرط بايد مصرف دارو قطع گردد.


مسموميت و درمان


تظاهرات باليني: تهوع، استفراغ، بي‌اشتهايي، تهييج ‌پذيري زياد، لرزش، اشكال در صحبت كردن، تاري ديد، لتارژي، نشانه‌هاي آنتي‌كولينرژيك، تشنج و احتمالاً اختلال در ريتم بطني ، از جمله torsade de pointes و فيبريلاسيون بطني.


توجه: اثرات CNS ناشي از افزايش غلظت دوپامين در مغز است.


درمان: بايد معده را فوراً شستشو داد و بيمار را وادار به استفراغ كرد. اين اعمال بايد با اقدامات حمايتي، تجويز مايعات زياد و در صورت لزوم ، با تزريق وريدي مايعات همراه باشد. براي افزايش دفع دارو مي‌توان از اسيدي كردن ادرار استفاده كرد. براي مقابله با مسموميت CNS مي‌توان فيزوستيگمين (2-1 ميلي‌گرم در فواصل 2-1 ساعت) به طور آهسته انفوزيون كرد. بيمار بايد به دقت تحت مراقبت باشد.

مکانیزم اثر

عوارض جانبي


اعصاب مرکزي : افسردگي، خستگي، کانفوزيون، سرگيجه، سايكوز، توهمات، اضطراب، تحريك‌پذيري، آتاكسي، بي‌خوابي، ضعف، سردرد، منگي، اشكال در تمركز حواس.


قلبي ـ عروقي: ادم محيطي ، كمي فشارخون در حالت ايستاده، نارسايي احتقاني قلب.


پوست: كبودي پوست (با مصرف دراز مدت).


دستگاه گوارش: بي‌اشتهايي، تهوع، يبوست، استفراغ، خشكي دهان.


ادراري ـ تناسلي: احتباس ادرار.


توجه: در صورت بروز واكنش حساسيت مفرط بايد مصرف دارو قطع گردد.


مسموميت و درمان


تظاهرات باليني: تهوع، استفراغ، بي‌اشتهايي، تهييج ‌پذيري زياد، لرزش، اشكال در صحبت كردن، تاري ديد، لتارژي، نشانه‌هاي آنتي‌كولينرژيك، تشنج و احتمالاً اختلال در ريتم بطني ، از جمله torsade de pointes و فيبريلاسيون بطني.


توجه: اثرات CNS ناشي از افزايش غلظت دوپامين در مغز است.


درمان: بايد معده را فوراً شستشو داد و بيمار را وادار به استفراغ كرد. اين اعمال بايد با اقدامات حمايتي، تجويز مايعات زياد و در صورت لزوم ، با تزريق وريدي مايعات همراه باشد. براي افزايش دفع دارو مي‌توان از اسيدي كردن ادرار استفاده كرد. براي مقابله با مسموميت CNS مي‌توان فيزوستيگمين (2-1 ميلي‌گرم در فواصل 2-1 ساعت) به طور آهسته انفوزيون كرد. بيمار بايد به دقت تحت مراقبت باشد.

فارماكوكینتیك

موارد منع مصرف و احتياط


موارد منع مصرف: حساسيت مفرط شناخته شده به دارو، بارداري، سنين باروري (اثرات تراتوژنيك و سمي بر رويان دارد).


موارد احتياط: سابقه بيماري كبدي، حملات تشنجي، سايكوز، بيماري كليوي، درماتيت اگزمايي عودكننده، صرع، بيماري قلبي - عروقي (بخصوص نارسايي احتقاني قلب ). ادم محيطي ، يا كمي فشارخون در حالت ايستاده (ممكن است باعث تشديد اين اختلال‌ها گردد).

سایر اطلاعات

طبقه‌بندي فارماكولوژيك: آمين حلقوي اوليه صناعي.


طبقه‌بندي درماني: ضد ويروس، ضد پاركينسون.


طبقه‌بندي مصرف در بارداري: رده C


ملاحظات اختصاصي


براي پيشگيري از كمي فشارخون در حالت ايستاده، بيمار بايد وضعيت خود را به آهستگي تغيير دهد (بخصوص هنگامي كه مي‌خواهد بايستد).


در صورت بروز بي‌خوابي، دارو چند ساعت قبل از خواب مصرف شود.


مصرف دارو به عنوان پيشگيري براي بيماراني توصيه شده كه نمي‌توانند واكسن ويروس آنفلوآنزا را تحمل كنند. كارخانه سازنده درمان پيشگيري را در موارد تماس نامعلوم يا مكرر با ويروس به مدت 90 روز توصيه مي‌كند.


نكات قابل توصيه به بيمار


اين دارو ممكن است هوشياري ذهني را مختل كند.


براي جذب بهتر دارو، آن را بعد از غذا مصرف كنيد.


در صورت مصرف اين دارو براي درمان پاركينسونيسم، آن را به طور ناگهاني قطع نكنيد، زيرا ممكن است حملات پاركينسوني به طور ناگهاني بروز كند.


از مصرف همزمان آمانتادين با فرآورده‌هاي حاوي الكل خودداري كنيد.


در صورت بروز عوارض جانبي، بخصوص سرگيجه، افسردگي، اضطراب، تهوع و احتباس ادرار، به پزشك اطلاع دهيد.


مصرف در سالمندان: بيماران سالمند به عوارض نورولوژيك دارو حساسيت بيشتري نشان مي‌دهند. تقسيم مقدار مصرف دارو به دو بار در روز ممكن است از بروز عوارض نورولوژيك آن بكاهد.


مصرف در كودكان: بي‌ضرري و اثربخشي مصرف آمانتادين در كودكان كوچكتر از يك سال ثابت نشده است.


مصرف در شيردهي: آمانتادين در شير مادر ترشح مي‌شود. در طي درمان با آمانتادين بايد از شير دادن به كودك خودداري شود.


مصرف در بارداري: در مورد مصرف اين دارو در بارداري مطالعات كنترل شده كافي وجود ندارد.

Amantadine Hydrochloride (Symmetrel)

SYMMETREL®
(amantadine hydrochloride, USP) Tablets and Syrup

DRUG DESCRIPTION

SYMMETREL (Amantadine Hydrochloride, USP) is designated generically as amantadine hydrochloride and chemically as 1-adamantanamine hydrochloride.

SYMMETREL®
  (Amantadine Hydrochloride) Structural Formula Illustration

Amantadine hydrochloride is a stable white or nearly white crystalline powder, freely soluble in water and soluble in alcohol and in chloroform.

Amantadine hydrochloride has pharmacological actions as both an anti-Parkinson and an antiviral drug.

SYMMETREL (amantadine hydrochloride) is available in tablets and syrup.

Each tablet intended for oral administration contains 100 mg amantadine hydrochloride and has the following inactive ingredients: hydroxypropyl methylcellulose, magnesium stearate, microcrystalline cellulose, sodium starch glycolate, FD&C Yellow No. 6.

SYMMETREL syrup contains 50 mg of amantadine hydrochloride per 5 mL and has the following inactive ingredients: artificial raspberry flavor, citric acid, methylparaben, propylparaben, and sorbitol solution.

What are the possible side effects of amantadine (Symmetrel)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

  • feeling short of breath, even with mild exertion;
  • swelling, rapid weight gain;
  • feeling depressed, agitated, or aggressive;
  • behavior changes, hallucinations, thoughts of hurting yourself;
  • urinating less than usual or not at all;
  • high fever, stiff muscles, confusion, sweating, fast or uneven...

Read All Potential Side Effects and See Pictures of Symmetrel »

What are the precautions when taking amantadine hydrochloride (Symmetrel)?

Before taking amantadine, tell your doctor or pharmacist if you are allergic to it; or to rimantadine; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: a certain type of eye disease (untreated closed-angle glaucoma).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: swelling of arms/legs (peripheral edema), heart problems (e.g., congestive heart failure), blood pressure problems (e.g., dizziness when standing), kidney disease, liver disease,...

Read All Potential Precautions of Symmetrel »

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

>

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

INDICATIONS

SYMMETREL (amantadine hydrochloride) is indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.

Influenza A Prophylaxis

SYMMETREL (amantadine hydrochloride) is indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because SYMMETREL (amantadine hydrochloride) does not completely prevent the host immune response to influenza A infection, individuals who take this drug may still develop immune responses to natural disease or vaccination and may be protected when later exposed to antigenically related viruses. Following vaccination during an influenza A outbreak, SYMMETREL (amantadine hydrochloride) prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.

Influenza A Treatment

SYMMETREL (amantadine hydrochloride) is also indicated in the treatment of uncomplicated respiratory tract illness caused by influenza A virus strains especially when administered early in the course of illness. There are no well-controlled clinical studies demonstrating that treatment with SYMMETREL (amantadine hydrochloride) will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.

There is no clinical evidence indicating that SYMMETREL (amantadine hydrochloride) is effective in the prophylaxis or treatment of viral respiratory tract illnesses other than those caused by influenza A virus strains.

The following points should be considered before initiating treatment or prophylaxis with SYMMETREL (amantadine hydrochloride) :

  • SYMMETREL (amantadine hydrochloride) is not a substitute for early vaccination on an annual basis as recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices.
  • Influenza viruses change over time. Emergence of resistance mutations could decrease drug effectiveness. Other factors (for example, changes in viral virulence) might also diminish clinical benefit of antiviral drugs. Prescribers should consider available information on influenza drug susceptibility patterns and treatment effects when deciding whether to use SYMMETREL (amantadine hydrochloride) .

Parkinson's Disease/Syndrome

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication. It is indicated in those elderly patients believed to develop parkinsonism in association with cerebral arteriosclerosis. In the treatment of Parkinson's disease, SYMMETREL (amantadine hydrochloride) is less effective than levodopa, (-)-3-(3,4- dihydroxyphenyl)-L-alanine, and its efficacy in comparison with the anticholinergic antiparkinson drugs has not yet been established.

Drug-Induced Extrapyramidal Reactions

SYMMETREL (amantadine hydrochloride) is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with SYMMETREL (amantadine hydrochloride) when used in patients with drug-induced extrapyramidal reactions, there is a lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs.

DOSAGE AND ADMINISTRATION

The dose of SYMMETREL (Amantadine Hydrochloride, USP) may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function (see Dosage for Impaired Renal Function).

Dosage for Prophylaxis and Treatment of Uncomplicated Influenza A Virus Illness

Adult

The adult daily dosage of SYMMETREL (amantadine hydrochloride) is 200 mg; two 100 mg tablets (or four teaspoonfuls of syrup) as a single daily dose. The daily dosage may be split into one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. If central nervous system effects develop in once-a-day dosage, a split dosage schedule may reduce such complaints. In persons 65 years of age or older, the daily dosage of SYMMETREL (amantadine hydrochloride) is 100 mg.

A 100 mg daily dose has also been shown in experimental challenge studies to be effective as prophylaxis in healthy adults who are not at high risk for influenza-related complications. However, it has not been demonstrated that a 100 mg daily dose is as effective as a 200 mg daily dose for prophylaxis, nor has the 100 mg daily dose been studied in the treatment of acute influenza illness. In recent clinical trials, the incidence of central nervous system (CNS) side effects associated with the 100 mg daily dose was at or near the level of placebo. The 100 mg dose is recommended for persons who have demonstrated intolerance to 200 mg of SYMMETREL (amantadine hydrochloride) daily because of CNS or other toxicities.

Pediatric Patients: 1 yr.-9 yrs. of age

The total daily dose should be calculated on the basis of 2 to 4 mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.

9 yrs.-12 yrs. of age

The total daily dose is 200 mg given as one tablet of 100 mg (or two teaspoonfuls of syrup) twice a day. The 100 mg daily dose has not been studied in this pediatric population. Therefore, there are no data which demonstrate that this dose is as effective as or is safer than the 200 mg daily dose in this patient population.

Prophylactic dosing should be started in anticipation of an influenza A outbreak and before or after contact with individuals with influenza A virus respiratory tract illness.

SYMMETREL (amantadine hydrochloride) should be continued daily for at least 10 days following a known exposure. If SYMMETREL (amantadine hydrochloride) is used chemoprophylactically in conjunction with inactivated influenza A virus vaccine until protective antibody responses develop, then it should be administered for 2 to 4 weeks after the vaccine has been given. When inactivated influenza A virus vaccine is unavailable or contraindicated, SYMMETREL (amantadine hydrochloride) should be administered for the duration of known influenza A in the community because of repeated and unknown exposure.

Treatment of influenza A virus illness should be started as soon as possible, preferably within 24 to 48 hours after onset of signs and symptoms, and should be continued for 24 to 48 hours after the disappearance of signs and symptoms.

Dosage for Parkinsonism

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day when used alone. SYMMETREL (amantadine hydrochloride) has an onset of action usually within 48 hours.

The initial dose of SYMMETREL (amantadine hydrochloride) is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.

Patients initially deriving benefit from SYMMETREL (amantadine hydrochloride) not uncommonly experience a fall-off of effectiveness after a few months. Benefit may be regained by increasing the dose to 300 mg daily. Alternatively, temporary discontinuation of SYMMETREL (amantadine hydrochloride) for several weeks, followed by reinitiation of the drug, may result in regaining benefit in some patients. A decision to use other antiparkinson drugs may be necessary.

Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to SYMMETREL (amantadine hydrochloride) . When SYMMETREL (amantadine hydrochloride) or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When SYMMETREL (amantadine hydrochloride) and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. SYMMETREL (amantadine hydrochloride) should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When SYMMETREL (amantadine hydrochloride) is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of SYMMETREL (amantadine hydrochloride) .

Dosage for Drug-Induced Extrapyramidal Reactions

Adult

The usual dose of SYMMETREL (amantadine hydrochloride) is 100 mg twice a day. Occasionally, patients whose responses are not optimal with SYMMETREL (amantadine hydrochloride) at 200 mg daily may benefit from an increase up to 300 mg daily in divided doses.

Dosage for Impaired Renal Function

Depending upon creatinine clearance, the following dosage adjustments are recommended:

CREATININE CLEARANCE
(mL/min/1.73m2)
SYMMETREL DOSAGE
30-50 200 mg 1st day and 100 mg each day thereafter
15-29 200 mg 1st day followed by 100 mg on alternate days
< 15 200 mg every 7 days

The recommended dosage for patients on hemodialysis is 200 mg every 7 days.

HOW SUPPLIED

SYMMETREL (Amantadine Hydrochloride, USP) is available in light orange, convex curved, triangular shaped 100 mg tablets with “SYMMETREL (amantadine hydrochloride) ” debossed on one side and plain on the other side as follows:

Bottles of 100.......................NDC 63481-108-70

As a clear, colorless syrup [each 5 mL (1 teaspoonful) contains 50 mg amantadine hydrochloride] in:

16 oz. (480 mL) bottles.......................NDC 63481-205-16

Store at 25°C (77°F), excursions permitted to 15°-30°C (59°-86°F). [See USP Controlled Room Temperature].

Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).

Manufactured for: Endo Pharmaceuticals Inc. Chadds Ford, PA 19317. January, 2009

Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.

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