5-HT2 antagonist ritanserin in neuroleptic-induced parkinsonism: a double-blind comparison with orphenadrine and placebo

Several studies support the hypothesis of 5-HT (serotonin) involvement in the physiopathology of the extrapyramidal system. Ritanserin is a new compound with a high, selective, and long-lasting binding affinity for 5-HT2 receptors. A therapeutic effect of ritanserin has been reported in Parkinson's tremor and L-Dopa-induced dyskinesias but no effect was seen in essential tremor. In this double-blind comparative study with orphenadrine (150 mg daily p.o.) and placebo, ritanserin (30 mg daily p.o.) was administered to 36 schizophrenic outpatients who were being treated with neuroleptic drugs and who had parkinsonism. For a period of 3 weeks, the treatment was added to the antipsychotic therapy after a 7-day washout from previous antiparkinson medication. Psychopathology was rated weekly by the Brief Psychiatric Rating Scale and showed no significant changes during the trial. The Mindham Rating Scale was used to assess symptoms of parkinsonism; at week 3, ritanserin was superior to orphenadrine (p less than 0.03) and to placebo (p less than 0.01). The results confirm previous observations of the therapeutic efficacy of ritanserin on neuroleptic-induced parkinsonism, and support the hypothesis that serotonin influences extrapyramidal physiopathology.