Delayed amantadine toxicity causing apparent progression of multiple sclerosis

Background: Amantadine is sometimes used to treat fatigue in multiple sclerosis. Objectives: To report a patient with secondary progressive multiple sclerosis (SPMS) who developed late-onset side effects of amantadine which were initially felt to represent a progression of her SPMS. Methods: A single retrospective case report. Results: Symptoms of cognitive deterioration, ataxia and hallucinations resolved completely on cessation of the amantadine she had been prescribed several years beforehand. Conclusion: Clinicians involved in the management of the symptoms of SPMS should be aware of the potential for cumulative side effects of drugs used to treat symptoms and consider their potential role in precipitating neurological deterioration.