Symmetrel (Amantadine Hydrochloride)
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Symmetrel (Amantadine Hydrochloride)

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.

SIDE EFFECTS

The adverse reactions reported most frequently at the recommended dose of SYMMETREL (amantadine hydrochloride) (5-10%) are: nausea, dizziness (lightheadedness), and insomnia.

Less frequently (1-5%) reported adverse reactions are: depression, anxiety and irritability, hallucinations, confusion, anorexia, dry mouth, constipation, ataxia, livedo reticularis, peripheral edema, orthostatic hypotension, headache, somnolence, nervousness, dream abnormality, agitation, dry nose, diarrhea and fatigue.

Infrequently (0.1-1%) occurring adverse reactions are: congestive heart failure, psychosis, urinary retention, dyspnea, skin rash, vomiting, weakness, slurred speech, euphoria, thinking abnormality, amnesia, hyperkinesia, hypertension, decreased libido, and visual disturbance, including punctate subepithelial or other corneal opacity, corneal edema, decreased visual acuity, sensitivity to light, and optic nerve palsy.

Rare (less than 0.1%) occurring adverse reactions are: instances of convulsion, leukopenia, neutropenia, eczematoid dermatitis, oculogyric episodes, suicidal attempt, suicide, and suicidal ideation (see WARNINGS).

Other adverse reactions reported during postmarketing experience with SYMMETREL (amantadine hydrochloride) usage include:

Nervous System/Psychiatric

coma, stupor, delirium, hypokinesia, hypertonia, delusions, aggressive behavior, paranoid reaction, manic reaction, involuntary muscle contractions, gait abnormalities, paresthesia, EEG changes, and tremor. Abrupt discontinuation may also precipitate delirium, agitation, delusions, hallucinations, paranoid reaction, stupor, anxiety, depression and slurred speech;

Cardiovascular

cardiac arrest, arrhythmias including malignant arrhythmias, hypotension, and tachycardia;

Respiratory

acute respiratory failure, pulmonary edema, and tachypnea;

Gastrointestinal

dysphagia;

Hematologic

leukocytosis; agranulocytosis

Special Senses

keratitis and mydriasis;

Skin and Appendages

pruritus and diaphoresis;

Miscellaneous

neuroleptic malignant syndrome (see WARNINGS), allergic reactions including anaphylactic reactions, edema, fever, pathological gambling, increased libido including hypersexuality, and impulse control symptoms.

Laboratory Test

elevated: CPK, BUN, serum creatinine, alkaline phosphatase, LDH, bilirubin, GGT, SGOT, and SGPT.

Read the Symmetrel (amantadine hydrochloride) Side Effects Center for a complete guide to possible side effects »

DRUG INTERACTIONS

Careful observation is required when SYMMETREL (amantadine hydrochloride) is administered concurrently with central nervous system stimulants.

Agents with anticholinergic properties may potentiate the anticholinergic-like side effects of amantadine.

Coadministration of thioridazine has been reported to worsen the tremor in elderly patients with Parkinson's disease, however, it is not known if other phenothiazines produce a similar response. Coadministration of Dyazide (triamterene/hydrochlorothiazide) resulted in a higher plasma amantadine concentration in a 61-year-old man receiving SYMMETREL (Amantadine Hydrochloride, USP) 100 mg TID for Parkinson's disease.1 It is not known which of the components of Dyazide contributed to the observation or if related drugs produce a similar response.

Coadministration of quinine or quinidine with amantadine was shown to reduce the renal clearance of amantadine by about 30%.

The concurrent use of SYMMETREL (amantadine hydrochloride) with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of the potential for interference between these products, LAIV should not be administered within 2 weeks before or 48 hours after administration of SYMMETREL (amantadine hydrochloride) , unless medically indicated. The concern about possible interference arises from the potential for antiviral drugs to inhibit replication of live vaccine virus. Trivalent inactivated influenza vaccine can be administered at any time relative to use of SYMMETREL (amantadine hydrochloride) .

REFERENCES

1. W.W. Wilson and A.H. Rajput, Amantadine-Dyazide Interaction, Can. Med. Assoc. J. 129:974- 975, 1983.

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

WARNINGS

Deaths

Deaths have been reported from overdose with SYMMETREL (amantadine hydrochloride) . The lowest reported acute lethal dose was 1 gram. Acute toxicity may be attributable to the anticholinergic effects of amantadine. Drug overdose has resulted in cardiac, respiratory, renal or central nervous system toxicity. Cardiac dysfunction includes arrhythmia, tachycardia and hypertension (see OVERDOSAGE).

Suicide Attempts

Suicide attempts, some of which have been fatal, have been reported in patients treated with SYMMETREL (amantadine hydrochloride) , many of whom received short courses for influenza treatment or prophylaxis. The incidence of suicide attempts is not known and the pathophysiologic mechanism is not understood. Suicide attempts and suicidal ideation have been reported in patients with and without prior history of psychiatric illness. SYMMETREL (amantadine hydrochloride) can exacerbate mental problems in patients with a history of psychiatric disorders or substance abuse. Patients who attempt suicide may exhibit abnormal mental states which include disorientation, confusion, depression, personality changes, agitation, aggressive behavior, hallucinations, paranoia, other psychotic reactions, and somnolence or insomnia. Because of the possibility of serious adverse effects, caution should be observed when prescribing SYMMETREL (amantadine hydrochloride) to patients being treated with drugs having CNS effects, or for whom the potential risks outweigh the benefit of treatment.

CNS Effects

Patients with a history of epilepsy or other “seizures” should be observed closely for possible increased seizure activity.

Patients receiving SYMMETREL (amantadine hydrochloride) who note central nervous system effects or blurring of vision should be cautioned against driving or working in situations where alertness and adequate motor coordination are important.

Other

Patients with a history of congestive heart failure or peripheral edema should be followed closely as there are patients who developed congestive heart failure while receiving SYMMETREL (amantadine hydrochloride) .

Patients with Parkinson's disease improving on SYMMETREL (amantadine hydrochloride) should resume normal activities gradually and cautiously, consistent with other medical considerations, such as the presence of osteoporosis or phlebothrombosis.

Because SYMMETREL (amantadine hydrochloride) has anticholinergic effects and may cause mydriasis, it should not be given to patients with untreated angle closure glaucoma.

PRECAUTIONS

SYMMETREL (amantadine hydrochloride) should not be discontinued abruptly in patients with Parkinson's disease since a few patients have experienced a parkinsonian crisis, i.e., a sudden marked clinical deterioration, when this medication was suddenly stopped. The dose of anticholinergic drugs or of SYMMETREL (amantadine hydrochloride) should be reduced if atropine-like effects appear when these drugs are used concurrently. Abrupt discontinuation may also precipitate delirium, agitation, delusions, hallucinations, paranoid reaction, stupor, anxiety, depression and slurred speech.

Neuroleptic Malignant Syndrome (NMS)

Sporadic cases of possible Neuroleptic Malignant Syndrome (NMS) have been reported in association with dose reduction or withdrawal of SYMMETREL (amantadine hydrochloride) therapy. Therefore, patients should be observed carefully when the dosage of SYMMETREL (amantadine hydrochloride) is reduced abruptly or discontinued, especially if the patient is receiving neuroleptics.

NMS is an uncommon but life-threatening syndrome characterized by fever or hyperthermia; neurologic findings including muscle rigidity, involuntary movements, altered consciousness; mental status changes; other disturbances such as autonomic dysfunction, tachycardia, tachypnea, hyper- or hypotension; laboratory findings such as creatine phosphokinase elevation, leukocytosis, myoglobinuria, and increased serum myoglobin.

The early diagnosis of this condition is important for the appropriate management of these patients. Considering NMS as a possible diagnosis and ruling out other acute illnesses (e.g., pneumonia, systemic infection, etc.) is essential. This may be especially complex if the clinical presentation includes both serious medical illness and untreated or inadequately treated extrapyramidal signs and symptoms (EPS). Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever and primary central nervous system (CNS) pathology.

The management of NMS should include: 1) intensive symptomatic treatment and medical monitoring, and 2) treatment of any concomitant serious medical problems for which specific treatments are available. Dopamine agonists, such as bromocriptine, and muscle relaxants, such as dantrolene are often used in the treatment of NMS, however, their effectiveness has not been demonstrated in controlled studies.

Renal disease

Because SYMMETREL (amantadine hydrochloride) is mainly excreted in the urine, it accumulates in the plasma and in the body when renal function declines. Thus, the dose of SYMMETREL (amantadine hydrochloride) should be reduced in patients with renal impairment and in individuals who are 65 years of age or older (see DOSAGE AND ADMINISTRATION; Dosage for Impaired Renal Function).

Liver disease

Care should be exercised when administering SYMMETREL (amantadine hydrochloride) to patients with liver disease. Rare instances of reversible elevation of liver enzymes have been reported in patients receiving SYMMETREL (amantadine hydrochloride) , though a specific relationship between the drug and such changes has not been established.

Melanoma

Epidemiological studies have shown that patients with Parkinson's disease have a higher risk (2-to approximately 6-fold higher) of developing melanoma than the general population. Whether the increased risk observed was due to Parkinson's disease or other factors, such as drugs used to treat Parkinson's disease, is unclear.

For the reasons stated above, patients and providers are advised to monitor for melanomas frequently and on a regular basis when using SYMMETREL (amantadine hydrochloride) for any indication. Ideally, periodic skin examinations should be performed by appropriately qualified individuals (e.g., dermatologists).

Other

The dose of SYMMETREL (amantadine hydrochloride) may need careful adjustment in patients with congestive heart failure, peripheral edema, or orthostatic hypotension. Care should be exercised when administering SYMMETREL (amantadine hydrochloride) to patients with a history of recurrent eczematoid rash, or to patients with psychosis or severe psychoneurosis not controlled by chemotherapeutic agents.

Serious bacterial infections may begin with influenza-like symptoms or may coexist with or occur as complications during the course of influenza. SYMMETREL (amantadine hydrochloride) has not been shown to prevent such complications.

Carcinogenesis and Mutagenesis

Long-term in vivo animal studies designed to evaluate the carcinogenic potential of SYMMETREL (amantadine hydrochloride) have not been performed. In several in vitro assays for gene mutation, SYMMETREL (amantadine hydrochloride) did not increase the number of spontaneously observed mutations in four strains of Salmonella typhimurium (Ames Test) or in a mammalian cell line (Chinese Hamster Ovary cells) when incubations were performed either with or without a liver metabolic activation extract. Further, there was no evidence of chromosome damage observed in an in vitro test using freshly derived and stimulated human peripheral blood lymphocytes (with and without metabolic activation) or in an in vivo mouse bone marrow micronucleus test (140-550 mg/kg; estimated human equivalent doses of 11.7-45.8 mg/kg based on body surface area conversion).

Impairment of Fertility

The effect of amantadine on fertility has not been adequately tested, that is, in a study conducted under Good Laboratory Practice (GLP) and according to current recommended methodology. In a three litter, non-GLP, reproduction study in rats, Symmetrel (amantadine hydrochloride) at a dose of 32 mg/kg/day (equal to the maximum recommended human dose on a mg/m2 basis) administered to both males and females slightly impaired fertility. There were no effects on fertility at a dose level of 10 mg/kg/day (or 0.3 times the maximum recommended human dose on a mg/m2 basis); intermediate doses were not tested.

Failed fertility has been reported during human in vitro fertilization (IVF) when the sperm donor ingested amantadine 2 weeks prior to, and during the IVF cycle.

Pregnancy Category C

The effect of amantadine on embryofetal and peri-postnatal development has not been adequately tested, that is, in studies conducted under Good Laboratory Practice (GLP) and according to current recommended methodology. However, in two non-GLP studies in rats in which females were dosed from 5 days prior to mating to Day 6 of gestation or on Days 7-14 of gestation, Symmetrel (amantadine hydrochloride) produced increases in embryonic death at an oral dose of 100 mg/kg (or 3 times the maximum recommended human dose on a mg/m2 basis). In the non-GLP rat study in which females were dosed on Days 7-14 of gestation, there was a marked increase in severe visceral and skeletal malformations at oral doses of 50 and 100 mg/kg (or 1.5 and 3 times, respectively, the maximum recommended human dose on a mg/m2 basis). The no-effect dose for teratogenicity was 37 mg/kg (equal to the maximum recommended human dose on a mg/m2 basis). The safety margins reported may not accurately reflect the risk considering the questionable quality of the study on which they are based. There are no adequate and well-controlled studies in pregnant women. Human data regarding teratogenicity after maternal use of amantadine is scarce. Tetralogy of Fallot and tibial hemimelia (normal karyotype) occurred in an infant exposed to amantadine during the first trimester of pregnancy (100 mg P.O. for 7 days during the 6th and 7th week of gestation). Cardiovascular maldevelopment (single ventricle with pulmonary atresia) was associated with maternal exposure to amantadine (100 mg/d) administered during the first 2 weeks of pregnancy. SYMMETREL (amantadine hydrochloride) should be used during pregnancy only if the potential benefit justifies the potential risk to the embryo or fetus.

Nursing Mothers

SYMMETREL (amantadine hydrochloride) is excreted in human milk. Use is not recommended in nursing mothers.

Pediatric Use

The safety and efficacy of SYMMETREL (amantadine hydrochloride) in newborn infants and infants below the age of 1 year have not been established.

Usage in the Elderly

Because SYMMETREL (amantadine hydrochloride) is primarily excreted in the urine, it accumulates in the plasma and in the body when renal function declines. Thus, the dose of SYMMETREL (amantadine hydrochloride) should be reduced in patients with renal impairment and in individuals who are 65 years of age or older. The dose of SYMMETREL (amantadine hydrochloride) may need reduction in patients with congestive heart failure, peripheral edema, or orthostatic hypotension (see DOSAGE AND ADMINISTRATION).

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

OVERDOSE

Deaths have been reported from overdose with SYMMETREL (amantadine hydrochloride) . The lowest reported acute lethal dose was 1 gram. Because some patients have attempted suicide by overdosing with amantadine, prescriptions should be written for the smallest quantity consistent with good patient management.

Acute toxicity may be attributable to the anticholinergic effects of amantadine. Drug overdose has resulted in cardiac, respiratory, renal or central nervous system toxicity. Cardiac dysfunction includes arrhythmia, tachycardia and hypertension. Pulmonary edema and respiratory distress (including adult respiratory distress syndrome - ARDS) have been reported; renal dysfunction including increased BUN, decreased creatinine clearance and renal insufficiency can occur. Central nervous system effects that have been reported include insomnia, anxiety, agitation, aggressive behavior, hypertonia, hyperkinesia, ataxia, gait abnormality, tremor, confusion, disorientation, depersonalization, fear, delirium, hallucinations, psychotic reactions, lethargy, somnolence and coma. Seizures may be exacerbated in patients with prior history of seizure disorders. Hyperthermia has also been observed in cases where a drug overdose has occurred.

There is no specific antidote for an overdose of SYMMETREL (amantadine hydrochloride) . However, slowly administered intravenous physostigmine in 1 and 2 mg doses in an adult2 at 1- to 2-hour intervals and 0.5 mg doses in a child3 at 5- to 10-minute intervals up to a maximum of 2 mg/hour have been reported to be effective in the control of central nervous system toxicity caused by amantadine hydrochloride. For acute overdosing, general supportive measures should be employed along with immediate gastric lavage or induction of emesis. Fluids should be forced, and if necessary, given intravenously. The pH of the urine has been reported to influence the excretion rate of SYMMETREL (amantadine hydrochloride) . Since the excretion rate of SYMMETREL (amantadine hydrochloride) increases rapidly when the urine is acidic, the administration of urine acidifying drugs may increase the elimination of the drug from the body. The blood pressure, pulse, respiration and temperature should be monitored. The patient should be observed for hyperactivity and convulsions; if required, sedation, and anticonvulsant therapy should be administered. The patient should be observed for the possible development of arrhythmias and hypotension; if required, appropriate antiarrhythmic and antihypotensive therapy should be given. Electrocardiographic monitoring may be required after ingestion, since malignant tachyarrhythmias can appear after overdose.

Care should be exercised when administering adrenergic agents, such as isoproterenol, to patients with a SYMMETREL (amantadine hydrochloride) overdose, since the dopaminergic activity of SYMMETREL (amantadine hydrochloride) has been reported to induce malignant arrhythmias.

The blood electrolytes, urine pH and urinary output should be monitored. If there is no record of recent voiding, catheterization should be done.

CONTRAINDICATIONS

SYMMETREL (amantadine hydrochloride) is contraindicated in patients with known hypersensitivity to amantadine hydrochloride or to any of the other ingredients in SYMMETREL (amantadine hydrochloride) .

REFERENCES

2. D.F. Casey, N. Engl. J. Med. 298:516, 1978.

3. C.D. Berkowitz, J. Pediatr. 95:144, 1979.

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

CLINICAL PHARMACOLOGY

Pharmacodynamics

Mechanism of Action: Antiviral

The mechanism by which amantadine exerts its antiviral activity is not clearly understood. It appears to mainly prevent the release of infectious viral nucleic acid into the host cell by interfering with the function of the transmembrane domain of the viral M2 protein. In certain cases, amantadine is also known to prevent virus assembly during virus replication. It does not appear to interfere with the immunogenicity of inactivated influenza A virus vaccine.

Antiviral Activity

Amantadine inhibits the replication of influenza A virus isolates from each of the subtypes, i.e., H1N1, H2N2 and H3N2. It has very little or no activity against influenza B virus isolates. A quantitative relationship between the in vitro susceptibility of influenza A virus to amantadine and the clinical response to therapy has not been established in man. Sensitivity test results, expressed as the concentration of amantadine required to inhibit by 50% the growth of virus (ED50) in tissue culture vary greatly (from 0.1 µg/mL to 25.0 µg/mL) depending upon the assay protocol used, size of virus inoculum, isolates of influenza A virus strains tested, and the cell type used. Host cells in tissue culture readily tolerated amantadine up to a concentration of 100 µg/mL.

Drug Resistance

Influenza A variants with reduced in vitro sensitivity to amantadine have been isolated from epidemic strains in areas where adamantane derivatives are being used. Influenza viruses with reduced in vitro sensitivity have been shown to be transmissible and to cause typical influenza illness. The quantitative relationship between the in vitro sensitivity of influenza A variants to amantadine and the clinical response to therapy has not been established.

Mechanism of Action: Parkinson's Disease

The mechanism of action of amantadine in the treatment of Parkinson's disease and drug-induced extrapyramidal reactions is not known. Data from earlier animal studies suggest that SYMMETREL (amantadine hydrochloride) may have direct and indirect effects on dopamine neurons. More recent studies have demonstrated that amantadine is a weak, non-competitive NMDA receptor antagonist (Ki = 10µM). Although amantadine has not been shown to possess direct anticholinergic activity in animal studies, clinically, it exhibits anticholinergic-like side effects such as dry mouth, urinary retention, and constipation.

Pharmacokinetics

SYMMETREL (amantadine hydrochloride) is well absorbed orally. Maximum plasma concentrations are directly related to dose for doses up to 200 mg/day. Doses above 200 mg/day may result in a greater than proportional increase in maximum plasma concentrations. It is primarily excreted unchanged in the urine by glomerular filtration and tubular secretion. Eight metabolites of amantadine have been identified in human urine. One metabolite, an N-acetylated compound, was quantified in human urine and accounted for 5-15% of the administered dose. Plasma acetylamantadine accounted for up to 80% of the concurrent amantadine plasma concentration in 5 of 12 healthy volunteers following the ingestion of a 200 mg dose of amantadine. Acetylamantadine was not detected in the plasma of the remaining seven volunteers. The contribution of this metabolite to efficacy or toxicity is not known.

There appears to be a relationship between plasma amantadine concentrations and toxicity. As concentration increases, toxicity seems to be more prevalent, however, absolute values of amantadine concentrations associated with adverse effects have not been fully defined.

Amantadine pharmacokinetics were determined in 24 normal adult male volunteers after the oral administration of a single amantadine hydrochloride 100 mg soft gel capsule. The mean ± SD maximum plasma concentration was 0.22 ± 0.03 µg/mL (range: 0.18 to 0.32 µg/mL). The time to peak concentration was 3.3 ± 1.5 hours (range: 1.5 to 8.0 hours). The apparent oral clearance was 0.28 ± 0.11 L/hr/kg (range: 0.14 to 0.62 L/hr/kg). The half-life was 17 ± 4 hours (range: 10 to 25 hours). Across other studies, amantadine plasma half-life has averaged 16 ± 6 hours (range: 9 to 31 hours) in 19 healthy volunteers.

After oral administration of a single dose of 100 mg amantadine syrup to five healthy volunteers, the mean ± SD maximum plasma concentration Cmax was 0.24 ± 0.04 µg/mL and ranged from 0.18 to 0.28 µg/mL. After 15 days of amantadine 100 mg b.i.d., the Cmax was 0.47 ± 0.11 µg/mL in four of the five volunteers. The administration of amantadine tablets as a 200 mg single dose to 6 healthy subjects resulted in a Cmax of 0.51 ± 0.14 µg/mL. Across studies, the time to Cmax (Tmax) averaged about 2 to 4 hours.

Plasma amantadine clearance ranged from 0.2 to 0.3 L/hr/kg after the administration of 5 mg to 25 mg intravenous doses of amantadine to 15 healthy volunteers.

In six healthy volunteers, the ratio of amantadine renal clearance to apparent oral plasma clearance was 0.79 ± 0.17 (mean ± SD).

The volume of distribution determined after the intravenous administration of amantadine to 15 healthy subjects was 3 to 8 L/kg, suggesting tissue binding. Amantadine, after single oral 200 mg doses to 6 healthy young subjects and to 6 healthy elderly subjects has been found in nasal mucus at mean ± SD concentrations of 0.15 ± 0.16, 0.28 ± 0.26, and 0.39 ± 0.34 µg/g at 1, 4, and 8 hours after dosing, respectively. These concentrations represented 31 ± 33%, 59 ± 61%, and 95 ± 86% of the corresponding plasma amantadine concentrations. Amantadine is approximately 67% bound to plasma proteins over a concentration range of 0.1 to 2.0 µg/mL. Following the administration of amantadine 100 mg as a single dose, the mean ± SD red blood cell to plasma ratio ranged from 2.7 ± 0.5 in 6 healthy subjects to 1.4 ± 0.2 in 8 patients with renal insufficiency.

The apparent oral plasma clearance of amantadine is reduced and the plasma half-life and plasma concentrations are increased in healthy elderly individuals age 60 and older. After single dose administration of 25 to 75 mg to 7 healthy, elderly male volunteers, the apparent plasma clearance of amantadine was 0.10 ± 0.04 L/hr/kg (range 0.06 to 0.17 L/hr/kg) and the half-life was 29 ± 7 hours (range 20 to 41 hours). Whether these changes are due to decline in renal function or other age related factors is not known.

In a study of young healthy subjects (n=20), mean renal clearance of amantadine, normalized for body mass index, was 1.5 fold higher in males compared to females (p < 0.032).

Compared with otherwise healthy adult individuals, the clearance of amantadine is significantly reduced in adult patients with renal insufficiency. The elimination half-life increases two to three fold or greater when creatinine clearance is less than 40 mL/min/1.73 m2 and averages eight days in patients on chronic maintenance hemodialysis. Amantadine is removed in negligible amounts by hemodialysis.

The pH of the urine has been reported to influence the excretion rate of SYMMETREL (amantadine hydrochloride) . Since the excretion rate of SYMMETREL (amantadine hydrochloride) increases rapidly when the urine is acidic, the administration of urine acidifying drugs may increase the elimination of the drug from the body.

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

PATIENT INFORMATION

Patients should be advised of the following information:

Blurry vision and/or impaired mental acuity may occur.

Gradually increase physical activity as the symptoms of Parkinson's disease improve.

Avoid excessive alcohol usage, since it may increase the potential for CNS effects such as dizziness, confusion, lightheadedness and orthostatic hypotension.

Avoid getting up suddenly from a sitting or lying position. If dizziness or lightheadedness occurs, notify physician.

Notify physician if mood/mental changes, swelling of extremities, difficulty urinating and/or shortness of breath occur.

Do not take more medication than prescribed because of the risk of overdose. If there is no improvement in a few days, or if medication appears less effective after a few weeks, discuss with a physician.

Consult physician before discontinuing medication.

Seek medical attention immediately if it is suspected that an overdose of medication has been taken.

There have been reports of patients experiencing intense urges to gamble, increased sexual urges, and other intense urges, and the inability to control these urges while taking one or more of the medications that increase central dopaminergic tone and that are generally used for the treatment of Parkinson's disease, including SYMMETREL (amantadine hydrochloride) . Although it is not proven that the medications caused these events, these urges were reported to have stopped in some cases when the dose was reduced or the medication was stopped. Prescribers should ask patients about the development of new or increased gambling urges, sexual urges or other urges while being treated with SYMMETREL (amantadine hydrochloride) . Patients should inform their physician if they experience new or increased gambling urges, increased sexual urges or other intense urges while taking SYMMETREL (amantadine hydrochloride) . Physicians should consider dose reduction or stopping the medication if a patient develops such urges while taking SYMMETREL (amantadine hydrochloride) .

Last reviewed on RxList: 3/11/2009
This monograph has been modified to include the generic and brand name in many instances.

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PATIENT INFORMATION

Patients should be advised of the following information:

Blurry vision and/or impaired mental acuity may occur.

Gradually increase physical activity as the symptoms of Parkinson's disease improve.

Avoid excessive alcohol usage, since it may increase the potential for CNS effects such as dizziness, confusion, lightheadedness and orthostatic hypotension.

Avoid getting up suddenly from a sitting or lying position. If dizziness or lightheadedness occurs, notify physician.

Notify physician if mood/mental changes, swelling of extremities, difficulty urinating and/or shortness of breath occur.

Do not take more medication than prescribed because of the risk of overdose. If there is no improvement in a few days, or if medication appears less effective after a few weeks, discuss with a physician.

Consult physician before discontinuing medication.

Seek medical attention immediately if it is suspected that an overdose of medication has been taken.

There have been reports of patients experiencing intense urges to gamble, increased sexual urges, and other intense urges, and the inability to control these urges while taking one or more of the medications that increase central dopaminergic tone and that are generally used for the treatment of Parkinson's disease, including SYMMETREL (amantadine hydrochloride) . Although it is not proven that the medications caused these events, these urges were reported to have stopped in some cases when the dose was reduced or the medication was stopped. Prescribers should ask patients about the development of new or increased gambling urges, sexual urges or other urges while being treated with SYMMETREL (amantadine hydrochloride) . Patients should inform their physician if they experience new or increased gambling urges, increased sexual urges or other intense urges while taking SYMMETREL (amantadine hydrochloride) . Physicians should consider dose reduction or stopping the medication if a patient develops such urges while taking SYMMETREL (amantadine hydrochloride) .

Last reviewed on RxList: 3/11/2009
This monograph has been modified to include the generic and brand name in many instances.

Disclaimer

Symmetrel Consumer

IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.

AMANTADINE - ORAL

(a-MAN-ta-deen)

COMMON BRAND NAME(S): Symadine, Symmetrel

USES: Amantadine is used to prevent or treat a certain type of flu (influenza A). If you have been infected with the flu, this medication may help make your symptoms less severe and shorten the time it will take you to get better. Taking amantadine if you have been or will be exposed to the flu may help to prevent you from getting the flu. This medication is an antiviral that is believed to work by stopping growth of the flu virus. This medication is not a vaccine. To increase the chance that you will not get the flu, it is important to get a flu shot once a year at the beginning of every flu season, if possible.

Based on the recommendation from the Centers for Disease Control (CDC) in the US, amantadine should not be used to treat or prevent influenza A because the current influenza A virus in the United States and Canada is resistant to this medication. For more details, talk to your doctor or pharmacist.

Amantadine is also used to treat Parkinson's disease, as well as side effects caused by drugs (e.g., drug-induced extrapyramidal symptoms), chemicals, other medical conditions. In these cases, this medication may help to improve your range of motion and ability to exercise. For the treatment of these conditions, amantadine is believed to work by restoring the balance of natural chemicals (neurotransmitters) in the brain.

HOW TO USE: Take this medication by mouth with or without food, usually once or twice daily or as directed by your doctor. If you are taking this medication twice a day and have trouble sleeping after taking it, take the second dose several hours before bedtime.

If you are taking the syrup, measure the dose carefully with a medication spoon/cup.

Dosage is based on your medical condition and response to therapy. In children, the dosage is also based on body weight. Do not take more than prescribed by your doctor.

This medication works best when the amount of medicine in your body is kept at a constant level. Therefore, take this medication at evenly spaced intervals throughout the day and night.

If you are taking amantadine for a viral infection, begin taking it as soon as possible. Continue taking it until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping the medication too early may result in a relapse of the infection.

In Parkinson's disease, the effects of the medication may not be noticed for several weeks. Do not suddenly stop taking the medication because symptoms or side effects may worsen. Your doctor may want to reduce your dose gradually. This medication may not work as well after it has been taken for several months. Tell your doctor if this medication stops working well.

Disclaimer

Symmetrel Consumer (continued)

SIDE EFFECTS: Blurred vision, nausea, stomach upset, drowsiness, dizziness, headache, dry mouth, constipation, nervousness, or trouble sleeping may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: purplish-red blotchy spots on the skin, swelling of the ankles/feet, difficulty urinating, vision changes.

Tell your doctor immediately if any of these rare but very serious side effects occur: shortness of breath, mental/mood changes (such as depression, suicidal thoughts/attempts, compulsive behavior including urge to gamble), muscle stiffness, uncontrolled muscle movements, unusual sweating, fast heartbeat, unexplained fever, seizures.

A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the Symmetrel (amantadine hydrochloride) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: 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, mental/mood conditions (e.g., depression, psychosis), seizures, a certain skin condition (eczematoid dermatitis).

This drug may make you dizzy or drowsy or cause blurred vision. Do not drive, use machinery, or do any activity that requires alertness or clear vision until you are sure you can perform such activities safely. Avoid alcoholic beverages.

To minimize dizziness and lightheadedness, get up slowly when rising from a seated or lying position.

If you are taking this medication for Parkinson's disease, be careful not to overdo physical activity as your condition improves because this may increase your risk of falls. Consult your doctor about a plan to gradually increase your physical activity as symptoms improve.

Kidney function declines as you grow older. This medication is removed by the kidneys. Therefore, elderly people may be at a greater risk for side effects while taking this drug.

This medication should be used during pregnancy only if clearly needed. There are rare reports of heart defects in newborns whose mothers took amantadine during pregnancy. Discuss the risks and benefits with your doctor.

This drug passes into breast milk and may have undesirable effects on a nursing infant. Consult with your doctor before breast-feeding.

Disclaimer

Symmetrel Consumer (continued)

DRUG INTERACTIONS: Your healthcare professionals (e.g., doctor or pharmacist) may already be aware of any possible drug interactions and may be monitoring you for it. Do not start, stop or change the dosage of any medicine before checking with them first.

This drug should not be used with the following medication because a very serious interaction may occur: flu vaccine inhaled through the nose.

If you are currently using the medication listed above, tell your doctor or pharmacist before starting amantadine.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: anticholinergics (e.g., atropine), antihistamines (e.g., diphenhydramine), certain psychiatric medicines (phenothiazines such as thioridazine), quinidine, quinine, stimulants (like caffeine and decongestants commonly found in cough-and-cold products), triamterene/hydrochlorothiazide, trimethoprim/sulfamethoxazole.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly. Symptoms of overdose may include fast/irregular heartbeats, severe drowsiness, shortness of breath, change in the amount of urine, mental/mood changes (e.g., anxiety, aggression, confusion, hallucinations), seizures.

NOTES: Do not share this product with others.

People with Parkinson's disease may have an increased risk for developing skin cancer (melanoma). If you are taking this drug to treat Parkinson's disease, tell your doctor promptly if you notice a change in the appearance or size of moles or other unusual skin changes. Ask your doctor if you should have regular skin exams.

MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

STORAGE: Store at room temperature at 77 degrees F (25 degrees C) away from light and moisture. Brief storage between 59-86 degrees F (15-30 degrees C) is permitted. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

Information last revised April 2012. Copyright(c) 2012 First Databank, Inc.

Symmetrel Patient Information Including Side Effects

Brand Names: Symmetrel

Generic Name: amantadine (Pronunciation: a MAN ta deen)

What is amantadine (Symmetrel)?

Amantadine is an antiviral medication. It blocks the actions of viruses in your body.

Amantadine is used to treat and to prevent influenza A (a viral infection). There may be some flu seasons during which amantadine is not recommended because certain flu strains may be resistant to this drug.

Amantadine is also used to treat Parkinson's disease and "Parkinson-like" symptoms such as stiffness and shaking that may be caused by the use of certain drugs.

Amantadine may also be used for other purposes not listed in this medication guide.

Amantadine 100 mg-APH

red, imprinted with INV 211

Amantadine 100 mg-GG

red, imprinted with GG 634

Amantadine 100 mg-UDL

yellow, imprinted with C-122

Amantadine 100 mg-UPS

yellow, imprinted with C-122

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 heartbeats, rapid breathing, feeling like you might pass out;
  • restless muscle movements in your eyes, tongue, jaw, or neck; or
  • tremor (uncontrolled shaking).

Less serious side effects may include:

  • dizziness, drowsiness, headache;
  • sleep problems (insomnia), strange dreams;
  • feeling nervous;
  • nausea, diarrhea, constipation, loss of appetite;
  • dry mouth, dry nose; or
  • loss of balance or coordination.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. You may report side effects to FDA at 1-800-FDA-1088.

Read the Symmetrel (amantadine hydrochloride) Side Effects Center for a complete guide to possible side effects »

What is the most important information I should know about amantadine (Symmetrel)?

Do not use FluMist nasal influenza "live vaccine" while you are being treated with amantadine and for at least 48 hours after you stop taking amantadine. The nasal vaccine may not be as effective if you receive it while you are taking amantadine. Before taking amantadine, tell your doctor if you have received a nasal flu vaccine within the past 14 days.

Before taking amantadine, tell your doctor if you have epilepsy or other seizure disorder, congestive heart failure, kidney or liver disease, low blood pressure, eczema, glaucoma, or a history of mental illness, suicide attempt, or drug/alcohol addiction.

Amantadine can cause side effects that may impair your thinking, vision, or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

If you are taking amantadine to treat influenza A, take the medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated.

If you are taking amantadine to treat Parkinson symptoms, do not stop taking the medication without first talking to your doctor. If you stop taking amantadine suddenly, your condition may become worse.

You may have increased sexual urges, unusual urges to gamble, or other intense urges while taking this medication. Talk with your doctor if you believe you have any intense or unusual urges while taking amantadine.

Side Effects Centers

Symmetrel Patient Information including How Should I Take

What should I discuss with my healthcare provider before taking amantadine (Symmetrel)?

You should not use this medication if you are allergic to amantadine, or if you have received a nasal flu vaccine (FluMist) within the past 14 days.

If you have any of these other conditions, you may need a dose adjustment or special tests to safely take amantadine:

  • epilepsy or other seizure disorder;
  • congestive heart failure;
  • kidney disease;
  • liver disease;
  • low blood pressure or fainting;
  • eczema;
  • glaucoma; or
  • a history of mental illness, suicide attempt, or drug/alcohol addiction.

You may have increased sexual urges, unusual urges to gamble, or other intense urges while taking amantadine. It is not known whether the medicine actually causes this effect. Talk with your doctor if you believe you have any intense or unusual urges while taking amantadine.

Some people taking medicines for Parkinson's disease have developed skin cancer (melanoma). However, people with Parkinson's disease may have a higher risk than most people for developing melanoma. Talk to your doctor about your specific risk and what skin symptoms to watch for. You may need to have regular skin exams.

FDA pregnancy category C. It is not known whether this medication is harmful to an unborn baby. Before taking amantadine, tell your doctor if you are pregnant or plan to become pregnant during treatment.

Amantadine can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

How should I take amantadine (Symmetrel)?

Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label.

Take this medicine with a full glass of water.

Measure the liquid form of amantadine with a special dose-measuring spoon or cup, not a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist for one.

If you are taking amantadine to treat influenza A, start taking the medication within 24 to 48 hours after flu symptoms begin. Keep taking the medication for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated.

If you are taking amantadine to treat Parkinson symptoms, do not stop taking the medication without first talking to your doctor. If you stop taking amantadine suddenly, your condition may become worse.

Store amantadine at room temperature away from moisture and heat.

Side Effects Centers

Symmetrel Patient Information including If I Miss a Dose

What happens if I miss a dose (Symmetrel)?

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

What happens if I overdose (Symmetrel)?

Seek emergency medical attention if you think you have used too much of this medicine. An overdose of amantadine can be fatal.

Overdose symptoms may include fever, anxiety, severe headache, confusion, hallucinations, agitation, aggression, personality changes, tremor, problems with balance or walking, fast or uneven heart rate, urinating less than usual or not at all, trouble breathing, seizure (convulsion), or fainting.

What should I avoid while taking amantadine (Symmetrel)?

Do not use FluMist nasal influenza "live vaccine" while you are being treated with amantadine and for at least 48 hours after you stop taking amantadine. The nasal vaccine may not be as effective if you receive it while you are taking amantadine. Before taking amantadine, tell your doctor if you have received a nasal flu vaccine within the past 14 days.

Amantadine can cause side effects that may impair your vision, thinking, or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.

Avoid drinking alcohol. It can increase some of the side effects of amantadine.

Avoid taking diet pills, caffeine pills, or other stimulants (such as ADHD medications) without your doctor's advice. Taking a stimulant together with amantadine can increase your risk of unpleasant side effects.

What other drugs will affect amantadine (Symmetrel)?

Before taking amantadine, tell your doctor if you are using any of the following drugs:

  • atropine (Atreza, Sal-Tropine, and others);
  • dicyclomine (Bentyl);
  • glycopyrrolate (Robinul);
  • hyoscyamine (Anaspaz, Levbid, Levsin, Nulev, and others);
  • mepenzolate (Cantil);
  • methscopolamine (Pamine);
  • propantheline (Pro-Banthine);
  • scopolamine (Maldemar, Scopace, Transderm-Scop).
  • quinine (Qualaquin);
  • quinidine (Cardioquin, Quinaglute);
  • a diuretic (water pill) such as triamterene (Dyrenium), hydrochlorothiazide (HCTZ, Dyazide, HydroDiuril, Hyzaar, Lopressor, Vasoretic, Zestoretic), and others; or
  • phenothiazines such as prochlorperazine (Compazine), thioridazine (Mellaril), and others.

This list is not complete and there may be other drugs that can interact with amantadine. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Where can I get more information?

Your pharmacist can provide more information about amantadine.


Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2012 Cerner Multum, Inc. Version: 6.02. Revision date: 12/15/2010.

Your use of the content provided in this service indicates that you have read,understood and agree to the End-User License Agreement,which can be accessed by clicking on this link.

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Side Effects Centers

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