The Prevalence of Acute Extrapyramidal Signs and Symptoms in Patients Treated With Clozapine, Risperidone, and Conventional Antipsychotics

Background: Acute extrapyramidal side effects(EPS) are a common phenomenon of treatment with conventionalantipsychotics. Previous studies found that clozapine has littlepropensity to cause EPS, while risperidone produces some EPS, butat levels lower than those of conventional antipsychotics.

Method: We compared the prevalence and severityof EPS in patients treated with clozapine, risperidone, orconventional antipsychotics for at least 3 months. Our mainhypothesis was that there would be differences between the threetreatment groups with regard to akathisia, measured with theBarnes Akathisia Scale, and extrapyramidal motor side effects(rigidity, rigidity factor, tremor, salivation), measured withthe Simpson-Angus scale. Secondarily, we were interested inpossible differences between the three groups with respect to theanticholinergic comedication and the subjective impression of thepatients, measured with the van Putten scale.

Results: We studied 106 patients (41 patientstreated with clozapine, 23 patients with risperidone, and 42patients treated with conventional antipsychotics). The samplewas 57.5% male and had a mean ± SD age of 36.6±9.3 years. Themean dose of antipsychotics calculated in chlorpromazineequivalents was 425.6±197.1 mg/day in the clozapine group,4.7±2.1 mg/day in the risperidone group, and 476.5±476.9 mg/dayin the group treated with conventional antipsychotics. Thepoint-prevalence of akathisia was 7.3% in the clozapine group,13% in the risperidone group, and 23.8% in the group treated withconventional antipsychotics. The point-prevalence of rigidity andcogwheeling respectively was 4.9% and 2.4% in the clozapinegroup, 17.4% and 17.4% in the risperidone group, and 35.7% and26.2% in the group treated with conventional antipsychotics.

Conclusion: Our results indicate thatrisperidone is superior to conventional neuroleptics in that itcauses fewer EPS. In comparison to clozapine, risperidoneproduces EPS levels that are intermediate between clozapine andconventional antipsychotic drugs.