Amantadine-induced coma

Amantadine has found use primarily as an antiviral agent and in the symptomatic treatment of parkinsonism. However, the use of amantadine for the subjective alleviation of fatigue in multiple sclerosis and in the treatment of agitated aggressive behavior in the traumatic brain injured patient has also been described. Side effects of amantadine are primarily related to the central nervous system and include hallucinations, confusion, and nightmares. Toxic manifestations include acute psychosis, coma, cardiovascular toxicity, and death. Amantadine toxicity is a particular problem in patients with renal insufficiency because 90% of an oral dose is excreted unchanged in the urine. We present a case of amantadine-induced coma in a patient with multiple sclerosis and end-stage renal disease. Moreover, this degree of amantadine toxicity was profoundly apparent at a drug level usually not associated with such a severe presentation.