Snapshot A 66-year-old man presents to a movements disorder specialist for management of his Parkinson disease. The patient believes that his quality of life has improved while being on carbidopa-levodopa. He is able to engage in his activities of daily living with minimal trouble. However, he notices moments of involuntary movements while being on this medication regimen, which has been troubling for him. Physical examination is notable for mild bradykinesia and an episode of short-lived myoclonus. He is started on amantadine to help reduce these dyskinesias. Introduction Mechanism of action anti-viral effects prevents the release of the viral nucleic acid into the host cell by interfering with viral M2 protein anti-Parkinsonian effects increases dopamine release and decreases dopamine reuptake Mechanism of resistance altered M2 protein no longer recommended for chemoprophylaxis or treatment of influenza A infection Clinical use Parkinson disease Adverse effects ataxia livedo reticularis