Efficacy of maintenance use of anticholinergic agents.

Twenty-seven long-term psychiatric inpatients maintained on neuroleptics with concomitant antiparkinsonian medication were entered into a study in which anticholinergic medication was gradually withdrawn in a randomized double-blind within-subjects design. The extrapyramidal symptoms of each patient were compared when taking their usual anticholinergic medication, when taking placebo and when taking no antiparkinsonian drug. The relapse rate on no medication was 14%, and if patients relapsed on no medication they also relapsed on placebo. The relapse rate was not significantly different on active medication. Nor were there significant differences in ratings of parkinsonism or dyskinesia. The lack of difference between double-blind and overt withdrawal does not mean that studies that find a much higher relapse rate are necessarily unaffected by nonspecific factors, as significant unblinding may occur in clinical trials.