A drug used to treat infections caused by the influenza A virus. It blocks the ability of the virus to infect cells and to make more virus particles. It is also used to treat the symptoms of Parkinson disease. Amantidine hydrochloride is a type of antiviral agent.

The hydrochloride salt of amantadine, a synthetic tricyclic amine with antiviral, antiparkinsonian, and antihyperalgesic activities. Amantadine appears to exert its antiviral effect against the influenza A virus by interfering with the function of the transmembrane domain of the viral M2 protein, thereby preventing the release of infectious viral nucleic acids into host cells; furthermore, this agent prevents virus assembly during virus replication. Amantadine exerts its antiparkinsonian effects by stimulating the release of dopamine from striatal dopaminergic nerve terminals and inhibiting its pre-synaptic reuptake. This agent may also exert some anticholinergic effect through inhibition of N-methyl-D-aspartic acid (NMDA) receptor-mediated stimulation of acetylcholine, resulting in antihyperalgesia.