Amantadine Hydrochloride is an antiviral and an antiparkinsonian drug.Target: Influenza VirusAmantadine Hydrochloride is an antiviral that is used in the prophylactic or symptomatic treatment of influenza A. It is also used as an antiparkinsonian agent, to treat extrapyramidal reactions, and for postherpetic neuralgia. Amantadine Hydrochloride binding of M2, based on studies of a peptide representing the M2 transmembrane segment in dodecylphosphocholine micelles. Amantadine Hydrochloride competes with protons for binding to the deprotonated tetramer, thereby stabilizing the tetramer in a slightly altered conformation. This model accounts for the observed inhibition of proton flux by amantadine [1]. In contrast to most other described channel-blocking molecules, amantadine causes the channel gate of NMDA receptors to close more quickly. Amantadine Hydrochloride binding inhibits current flow through NMDA receptor channels but show that its main inhibitory action at pharmaceutically relevant concentrations results from stabilization of closed states of the channel [2].

References:
[1]. Salom, D., et al., pH-dependent tetramerization and amantadine binding of the transmembrane helix of M2 from the influenza A virus. Biochemistry, 2000. 39(46): p. 14160-70.
[2]. Blanpied, T.A., R.J. Clarke, and J.W. Johnson, Amantadine inhibits NMDA receptors by accelerating channel closure during channel block. J Neurosci, 2005. 25(13): p. 3312-22.