Rimantadine hydrochloride is a white to off-white crystalline powder which is freely soluble in water (50 mg/mL at 20°C). Chemically, rimantadine hydrochloride is alpha-methyltricyclo-[18.104.22.168/3.7]decane-1-methanamine hydrochloride, with an empirical formula of C 12 H 21 N•HCl, a molecular weight of 215.77.
Rimantadine interferes with the activity of the virus's genetic material, blocking an essential step in the the process of viral replication. The drug affects only certain susceptible strains of the influenza type A virus. 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 M 2 gene plays an important role in the susceptibility of influenza A virus to inhibition by rimantadine.
Action/Kinetics: May act early in the viral replication cycle, possibly by inhibiting the uncoating of the virus. A virus protein specified by the virion M2 gene may play an important role in the inhibition of the influenza A virus by rimantadine. Has little or no activity against influenza B virus. Plasma trough levels following 100 mg b.i.d. for 10 days range from 118 to 468 ng/mL; however, levels are higher in clients over the age of 70 years. Metabolized in the liver, and both unchanged drug (25%) and metabolites excreted through the urine.
Rimantadine is used for the prevention or treatment of infections with influenza A virus, especially for individuals at high-risk such as immunosuppressed patients and nursing home residents. It should not be used as a substitute for vaccination.