Differential memory function with dopaminergic versus anticholinergic treatment of drug-induced extrapyramidal symptoms.

Nine chronic schizophrenic patients being treated with high-potency antipsychotic medication and antiparkinsonian agents were enrolled in a double-blind, crossover trial comparing amantadine and trihexyphenidyl. Memory function was assessed with the Rey Auditory-Verbal Learning Test during each 6-week drug trial. The subjects performed significantly better while receiving amantadine. Examinations of computed tomographic studies of seven subjects revealed a significant inverse correlation between ventricle size and memory while they were taking trihexyphenidyl but not amantadine. This suggests that patients with underlying brain pathology may be particularly vulnerable to the memory-disrupting effects of anticholinergic agents.