Extrapyramidal Symptoms and Tolerability of Olanzapine Versus Haloperidol in the Acute Treatment of Schizophrenia

Background: A relative lack of extrapyramidal symptoms (EPS, i.e., the syndromes of dystonia, parkinsonism, akathisia, dyskinesia) is one criterion used to determine whether an antipsychotic is “atypical.” The extrapyramidal symptom profiles of the novel antipsychotic olanzapine and the conventional antipsychotic haloperidol were compared in a population of 2606 patients from three well-controlled prospective clinical trials.

Method: Extrapyramidal symptom data were analyzed for 1796 patients treated with olanzapine (5 to 20 mg/day) and 810 patients treated with haloperidol (5 to 20 mg/day) for up to 6 weeks of therapy. Patients were monitored weekly by three methods of extrapyramidal symptom assessment: (1) detection of extrapyramidal adverse events (signs and symptoms) by casual observation, nonprobing inquiry, and spontaneous report; (2) objective rating scale scores; and (3) use of concomitant anticholinergic medications. Emergence of EPS was assessed by (1) analysis of the incidence of extrapyramidal syndrome categories based on adverse events, (2) the incidence of extrapyramidal syndromes based on categorical analysis of rating scale scores, (3) analysis of mean maximum change in rating scale scores, and (4) categorical analysis of anticholinergic medication use. Outcome of EPS was assessed by (1) analysis of mean change in rating scale scores at endpoint and (2) mean anticholinergic use at endpoint.

Results: Olanzapine was statistically significantly (p=.014, p<.001) superior to haloperidol in all four analyses related to emergence of EPS and in the two analyses related to outcome. Furthermore, during acute treatment, statistically significantly fewer patients treated with olanzapine (0.3%) discontinued the study because of any extrapyramidal adverse event than patients treated with haloperidol (2.7%, p<.001).

Conclusion: Olanzapine exhibited a statistically significantly lower extrapyramidal symptom profile than the conventional antipsychotic haloperidol at comparably effective antipsychotic doses. The lower extrapyramidal symptom profile with olanzapine was evident despite statistically significantly more frequent use of anticholinergic drugs among haloperidol-treated patients. Fewer olanzapine-treated than haloperidol-treated patients discontinued because of EPS, suggesting that olanzapine should contribute to better compliance with longer term maintenance treatment, with minimal anticholinergic-associated events.