rimantadine

Rimantadine is a derivative of amantadine and shares its mechanism: the M2 ion channel of influenza A allows protons into the virion to trigger uncoating after endocytosis, and blocking it stops the release of viral RNA into the cytoplasm. Because influenza B lacks M2, these agents never had activity against it. Rimantadine is better tolerated than amantadine, with fewer central nervous system effects such as insomnia, dizziness, ataxia, and confusion, because it undergoes extensive hepatic metabolism rather than renal excretion; dosing is therefore reduced in hepatic impairment and in the elderly. Widespread M2 resistance conferred by a single S31N substitution emerged during the 2000s, and since then the adamantanes have not been recommended for treatment or prophylaxis of influenza; neuraminidase inhibitors and baloxavir are used instead. Unlike amantadine, rimantadine has no useful antiparkinsonian activity.