Amantadine hydrochloride, USP is designated chemically as 1-adamantanamine hydrochloride. Its molecular weight is 187.71 with molecular formula C10 H18 NCl
Amantadine hydrochloride, USP is stable white or nearly white crystalline powder, freely soluble in water and soluble in alcohol and in chloroform.
Amantadine hydrochloride, USP has pharmacological actions as both an anti-Parkinson and an antiviral drug.
Amantadine hydrochloride, USP is available as 100 mg capsules for oral administration. Inactive ingredients: corn starch, croscarmellose sodium, ethylcellulose, magnesium stearate, microcrystalline cellulose, and pregelatinized starch. The capsule shells and imprinting ink contain: ammonium hydroxide, FD&C Blue #1, FD&C Red #40, gelatin, methylparaben, propylene glycol, propylparaben, shellac, simethicone, sodium lauryl sulfate, and titanium dioxide.
Mechanism of Action
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 virus vaccine.
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 amantadine may have direct and indirect effects on dopamine neurons. More recent studies have demonstrated that amantadine is weak, non-competitive NMDA receptor antagonist (K1 10?M). 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.
INDICATIONS AND USAGE
Amantadine hydrochloride capsules, USP are indicated for the prophylaxis and treatment of signs and symptoms of infection caused by various strains of influenza virus. Amantadine hydrochloride capsules, USP are also indicated in the treatment of parkinsonism and drug-induced extrapyramidal reactions.
Amantadine hydrochloride capsules, USP are indicated for chemoprophylaxis against signs and symptoms of influenza virus infection. Because amantadine does not completely prevent the host immune response to influenza 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 outbreak, amantadine prophylaxis should be considered for the 2- to 4-week time period required to develop an antibody response
Drug-Induced Extrapyramidal Reactions
Amantadine hydrochloride, USP 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 lower incidence of these side effects than that observed with the anticholinergic antiparkinson drugs
Pregnancy Category C
DOSAGE AND ADMINISTRATION
The dose of amantadine hydrochloride capsules may need reduction in patients with congestive heart failure, peripheral edema, orthostatic hypotension, or impaired renal function
Dosage for Prophylaxis and Treatment of Uncomplicated Influenza Virus Illness
The adult daily dosage of amantadine hydrochloride capsules is 200 mg; two 100 mg capsules as single daily dose. The daily dosage may be split into one capsule of 100 mg twice day. If central nervous system effects develop in once-a-day dosage, 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.
1 yr. to yrs. of age
The total daily dose should be calculated on the basis of to mg/lb/day (4.4 to 8.8 mg/kg/day), but not to exceed 150 mg per day.
Dosage for Parkinsonism
The usual dose of amantadine hydrochloride capsules is 100 mg twice 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.