Treatment of phenothiazine-induced dyskinesia.

Previous experience indicated the possibility that a serotonin antagonist substance, was effective in relieving dyskinesia as a reaction to phenothiazine antipsychotic drugs. Since the substances used in the original observations did not become available on the United States market, a compound known to be a serotonin antagonist, cyproheptadine, which was readily available and safe, was used to treat three patients who had phenothiazine-induced dyskinesia. In these patients, cyproheptadine was definitely effective in relieving the dyskinesia over an extended period of time. Further controlled studies are required to confirm this report.