Amantadine-induced cortical myoclonus

Abstract

Myoclonus can be induced by many drugs, including antiparkinsonian drugs, such as levodopa and bromocriptine1; but although there has been one report of amantadine-induced “vocal” myoclonus,2 we have seen no reports of generalized myoclonus induced by amantadine. We describe three patients with amantadine-induced cortical myoclonus. A 87-year-old woman with chronic renal failure on hemodialysis developed generalized myoclonic jerking at the end of April 1999 and was admitted to our department on May 27. Amantadine hydrochloride (HCL), 100 mg/d, had been administered at another hospital since April 2 1999, along with prazosin HCL, atenolol, ticlopidine HCL and l-thyroxine. She was in a confused state. Severe, asymmetrical, and multifocal myoclonic jerking was seen in all extremities, and involved her neck, tongue, and face muscles. Her myoclonus and confusion disappeared about two weeks after the discontinuation of amantadine on June 1. The dosage of other drugs was not changed. The plasma level of amantadine was 3,198 ng/mL on admission, decreasing to 407 ng/mL on June 13 and 47 ng/mL by June 28. A 78-year-old woman with a 4-year history of PD (Hoehn and Yahr stage IV) developed mild, asymmetrical and multifocal myoclonic jerking of all extremities in November 1997. She had been taking 40 mg …