Amantadine
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Adeel Jamil, M.D. [2]
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Black Box Warning
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Warning Title
See full prescribing information for complete Boxed Warning.
Condition Name: (Content)
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Overview
Amantadine is a Adamantane, anticholinergic, antiparkinsonian that is FDA approved for the treatment of Influenza A, Influenza A prophylaxis, parkinson’s disease/syndrome, drug-Induced extrapyramidal reactions. There is a Black Box Warning for this drug as shown here. Common adverse reactions include [orthostatic hypotension], [peripheral edema], [constipation], [diarrhea], [loss of appetite], [nausea], [xerostomia], [ataxia], [confusion], [dizziness], [headache], [insomnia], [somnolence], [agitation], [anxiety], [depression]. [dream disorder], feeling nervous, [hallucinations], [irritability] and [fatigue]..
Adult Indications and Dosage
FDA-Labeled Indications and Dosage (Adult)
- Amantadine hydrochloride capsules are indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza A virus. Amantadine hydrochloride capsules are also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.
Influenza A Prophylaxis
- Amantadine hydrochloride capsules are indicated for chemoprophylaxis against signs and symptoms of influenza A virus infection. Because amantadine 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, amantadine prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response.
Influenza A Treatment
- Amantadine hydrochloride capsules are 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 amantadine hydrochloride capsules will avoid the development of influenza A virus pneumonitis or other complications in high risk patients.
- There is no clinical evidence indicating that amantadine hydrochloride capsules are 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 amantadine hydrochloride capsules.
- Amantadine hydrochloride capsules are 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 amantadine hydrochloride capsules.
Parkinson’s Disease/Syndrome
- Amantadine hydrochloride capsules are 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, amantadine 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
- Amantadine hydrochloride is indicated in the treatment of drug-induced extrapyramidal reactions. Although anticholinergic-type side effects have been noted with amantadine 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.
- =====Dosing Information=====
The dose of amantadine hydrochloride capsules 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 amantadine hydrochloride capsules is 200 mg; two 100 mg capsules as a single daily dose. The daily dosage may be split into one capsule of 100 mg 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 amantadine hydrochloride capsules 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 amantadine hydrochloride daily because of CNS or other toxicities.
Dosage for Parkinsonism Adult
The usual dose of amantadine hydrochloride capsules is 100 mg twice a day when used alone. Amantadine has an onset of action usually within 48 hours.
The initial dose of amantadine hydrochloride capsules 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 amantadine hydrochloride capsules 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 amantadine hydrochloride capsules 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 amantadine hydrochloride capsules 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 amantadine hydrochloride capsules. When amantadine hydrochloride capsules or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.
When amantadine and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. Amantadine hydrochloride capsules should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.
When amantadine 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 amantadine hydrochloride capsules.
Dosage for Drug Induced Extrapyramidal Reactions Adult
The usual dose of amantadine hydrochloride capsules is 100 mg twice a day. Occasionally, patients whose responses are not optimal with amantadine hydrochloride capsules 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:
table
The recommended dosage for patients on hemodialysis is 200 mg every 7 days.
Off-Label Use and Dosage (Adult)
Guideline-Supported Use
Condition 1
- Developed by: (Organisation)
- Class of Recommendation: (Class) (Link)
- Strength of Evidence: (Category A/B/C) (Link)
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Condition 2
- Developed by: (Organisation)
- Class of Recommendation: (Class) (Link)
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Non–Guideline-Supported Use
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Pediatric Indications and Dosage
FDA-Labeled Indications and Dosage (Pediatric)
Condition 1
- Dosing Information
1 yr. to 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. to 12 yrs. of age
The total daily dose is 200 mg given as one capsule of 100 mg 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.
Amantadine hydrochloride capsules should be continued daily for at least 10 days following a known exposure. If amantadine 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, amantadine hydrochloride capsules 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.
Off-Label Use and Dosage (Pediatric)
Guideline-Supported Use
Condition 1
- Developed by: (Organisation)
- Class of Recommendation: (Class) (Link)
- Strength of Evidence: (Category A/B/C) (Link)
- Dosing Information/Recommendation
- (Dosage)
Condition 2
- Developed by: (Organisation)
- Class of Recommendation: (Class) (Link)
- Strength of Evidence: (Category A/B/C) (Link)
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Non–Guideline-Supported Use
Condition 1
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Condition 2
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Condition 3
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Contraindications
- Amantadine hydrochloride capsules, USP are contraindicated in patients with known hypersensitivity to amantadine hydrochloride or to any of the other ingredients in Amantadine hydrochloride capsules, USP.
Warnings
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Warning Title
See full prescribing information for complete Boxed Warning.
Condition Name: (Content)
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Deaths
- Deaths have been reported from overdose with amantadine. 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.
Suicide Attempts
- Suicide attempts, some of which have been fatal, have been reported in patients treated with amantadine, 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. Amantadine 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 amantadine hydrochloride capsules 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 amantadine hydrochloride capsules 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 amantadine hydrochloride capsules.
- Patients with Parkinson’s disease improving on amantadine hydrochloride capsules should resume normal activities gradually and cautiously, consistent with other medical considerations, such as the presence of osteoporosis or phlebothrombosis.
- Because Amantadine Hydrochloride Capsules, USP has anticholinergic effects and may cause mydriasis, it should not be given to patients with untreated angle closure glaucoma.
Adverse Reactions
Clinical Trials Experience
- The adverse reactions reported most frequently at the recommended dose of amantadine (5 to 10%) are: nausea, dizziness (lightheadedness), and insomnia.
- Less frequently (1 to 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 to 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 amantadine 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;
- Nervous System/Psychiatric
- Cardiovascular
- Cardiac arrest, arrhythmias including malignant arrhythmias, hypotension, and tachycardia;
- Cardiovascular
- Respiratory
- Acute respiratory failure, pulmonary edema, and tachypnea;
- Respiratory
- Gastrointestinal
- Dysphagia;
- Gastrointestinal
- Hematologic
- Leukocytosis, agranulocytosis;
- Hematologic
- Special Senses
- Keratitis and mydriasis;
- Special Senses
- Skin and Appendages
- Pruritus and diaphoresis;
- Skin and Appendages
- Miscellaneous
- Neuroleptic malignant syndrome (see WARNINGS), allergic reactions including anaphylactic reactions, edema, fever, pathological gambling, increased libido including hypersexuality, and impulse control symptoms.
- Miscellaneous
- Laboratory Test
- Elevated: CPK, BUN, serum creatinine, alkaline phosphatase, LDH, bilirubin, GGT, SGOT, and SGPT.
- Laboratory Test
- (list/description of adverse reactions)
Postmarketing Experience
(Description)
Drug Interactions
- Drug 1
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- Drug 3
- Drug 4
- Drug 5
Drug 1
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Drug 2
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Drug 3
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Drug 4
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Drug 5
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Use in Specific Populations
Pregnancy
Pregnancy Category (FDA):
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Pregnancy Category (AUS):
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Labor and Delivery
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Nursing Mothers
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Pediatric Use
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Geriatic Use
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Gender
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Race
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Renal Impairment
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Hepatic Impairment
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Females of Reproductive Potential and Males
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Immunocompromised Patients
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Others
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Administration and Monitoring
Administration
(Oral/Intravenous/etc)
Monitoring
Condition 1
(Description regarding monitoring, from Warnings section)
Condition 2
(Description regarding monitoring, from Warnings section)
Condition 3
(Description regarding monitoring, from Warnings section)
IV Compatibility
Solution
Compatible
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Not Tested
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- Solution 2
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Variable
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Incompatible
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Y-Site
Compatible
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- Solution 2
- Solution 3
Not Tested
- Solution 1
- Solution 2
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Variable
- Solution 1
- Solution 2
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Incompatible
- Solution 1
- Solution 2
- Solution 3
Admixture
Compatible
- Solution 1
- Solution 2
- Solution 3
Not Tested
- Solution 1
- Solution 2
- Solution 3
Variable
- Solution 1
- Solution 2
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Incompatible
- Solution 1
- Solution 2
- Solution 3
Syringe
Compatible
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Not Tested
- Solution 1
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Variable
- Solution 1
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Incompatible
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TPN/TNA
Compatible
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Variable
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Incompatible
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Overdosage
- Deaths have been reported from overdose with amantadine. 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 amantadine. 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 amantadine. Since the excretion rate of amantadine 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 an amantadine overdose, since the dopaminergic activity of amantadine 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.
(Description)
Management
(Description)
Chronic Overdose
Signs and Symptoms
(Description)
Management
(Description)
Pharmacology
Amantadine
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Mechanism of Action
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Structure
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Pharmacodynamics
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Pharmacokinetics
Amantadine 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 to 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 mcg/mL (range: 0.18 to 0.32 mcg/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 mcg/mL and ranged from 0.18 to 0.28 mcg/mL. After 15 days of amantadine 100 mg b.i.d., the Cmax was 0.47 ± 0.11 mcg/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 mcg/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 mcg/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 mcg/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 amantadine. Since the excretion rate of amantadine increases rapidly when the urine is acidic, the administration of urine acidifying drugs may increase the elimination of the drug from the body.
Nonclinical Toxicology
(Description)
Clinical Studies
Condition 1
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Condition 2
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How Supplied
- Amantadine hydrochloride capsules, USP for oral administration are available as:
- 100 mg: Red capsules imprinted GG 634 and supplied as:
- NDC 51079-247-20 - Unit dose blister packages of 100 (10 cards of 10 capsules each).
Storage
- Store at 20° to 25°C (68° to 77°F).
Images
Drug Images
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Package and Label Display Panel
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Patient Counseling Information
(Patient Counseling Information)
Precautions with Alcohol
Alcohol-Amantadine interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.
Brand Names
- Symmetrel®
Look-Alike Drug Names
- amantadine® - amiodarone®
Drug Shortage Status
Price
References
The contents of this FDA label are provided by the National Library of Medicine.