Are prophylactic antiparkinson drugs necessary? A controlled study of procyclidine withdrawal.

Of 55 aftercare patients receiving long-term treatment with antipsychotic and antiparkinson (AP) drugs, 37 were switched to being given placebo, and 18 remained on a regimen of procyclidine hydrochloride. The dose of antipsychotic was kept constant. After three weeks extrapyramidal side effects (EPS) developed in 54% of those patients receiving placebo and in none of those receiving procyclidine (P less than .002): Twenty-seven percent of the placebo group had EPS without akinesia, and in the same percentage akinesia developed (P = .003). We believe the risk-benefit ratio favors the routine use of AP drugs for prophylaxis and maintenance so as to avoid misdiagnosing as psychopathology, unspontaneity due to akinesia, and to reduce unreliable pill-taking due to EPS.