Lithium induced cogwheel rigidity: treatment with amantadine.

Extrapyramidal side effects (EPS) as a result of treatment with lithium ion is an uncom· mon, but weil documented, phenomenon (Bien, 1976; Branchey et al., 1976; DiMascio et al., 1976; and Shopsin and Gershon, 1975). Such lithium induced cogwheel rigidity has been reported in the V.S. but has not been confirmed by European observers. Treatment of these particular lithium induced side effects has remained problematic. Bien (1976) reported one patient on lithium treatment whose cogwheel rigidity did not respond to either intramuscular benztropine, 4 mg, or diphenhydramine, 50 mg. Shopsin and Gershon (1975) gave intravenous benztropine, 4 mg, to nine patients on lithium treatment who exhibited cogwheel rigidity, and only two of their patients showed even minimal amelioration. We wish to report a single case of a young woman who developed EPS in association with lithium treatment, which responded minimally to benztropine and diphenhydramine, and markedly to amantadine.