indication

For the prophylaxis and treatment of illness caused by various strains of influenza A virus in adults.

pharmacology

Rimantadine, a cyclic amine, is a synthetic antiviral drug and a derivate of adamantane, like a similar drug amantadine. Rimantadine is inhibitory to the in vitro replication of influenza A virus isolates from each of the three antigenic subtypes (H1N1, H2H2 and H3N2) that have been isolated from man. Rimantadine has little or no activity against influenza B virus. Rimantadine does not appear to interfere with the immunogenicity of inactivated influenza A vaccine.

mechanism of action

The mechanism of action of rimantadine is not fully understood. Rimantadine appears to exert its inhibitory effect early in the viral replicative cycle, possibly inhibiting the uncoating of the virus. Genetic studies suggest that a virus protein specified by the virion M2 gene plays an important role in the susceptibility of influenza A virus to inhibition by rimantadine.

toxicity

Oral LD₅₀ in rats is 640 mg/kg. Overdoses of a related rug, amantadine, have been reported with adverse reactions consisting of agitation, hallucinations, cardiac arrhythmia and death.

biotransformation

Following oral administration, rimantadine is extensively metabolized in the liver with less than 25% of the dose excreted in the urine as unchanged drug. Glucuronidation and hydroxylation are the major metabolic pathways.

absorption

Well absorbed, with the tablet and syrup formulations being equally absorbed after oral administration.

half life

25 to 30 hours in young adults (22 to 44 years old). Approximately 32 hours in elderly (71 to 79 years old) and in patients with chronic liver disease. Approximately 13 to 38 hours in children (4 to 8 years old).

route of elimination

Following oral administration, rimantadine is extensively metabolized in the liver with less than 25% of the dose excreted in the urine as unchanged drug.