Amantadine was first used for the treatment of influenza A. After antiviral properties were initially reported in 1963, amantadine received approval for prophylaxis against the influenza virus A in 1976. However, amantadine-resistant influenza viruses were first reported during the 1980 influenza A epidemic and resistance frequency continued to rise into the early 2000s. Currently, amantadine is no longer recommended for the treatment of influenza A due to a high level of amantadine resistance among circulating influenza A viruses. In 1973, the FDA approved amantadine for use in the treatment of Parkinson's disease. In 2017, the extended release formulation was approved for use in the treatment of levodopa-induced dyskinesia. Off-label uses include improvement of fatigue in multiple sclerosis and accelerating the rate of functional recovery and arousal following a brain injury.