Objective: The aim of this cross-sectional study was to investigate the degree and frequency of prolactin (PRL) elevation and related symptoms in patients treated with 3 different atypical antipsychotics: clozapine, olanzapine, and risperidone.
Method: Twenty-eight patients receiving clozapine, 29 patients receiving olanzapine, and 18 patients receiving risperidone (all meeting DSM-IV criteria for schizophrenia, schizophreni-form disorder, or schizoaffective disorder) were studied. The median daily dose was 400 mg of clozapine, 10 mg of olanzapine, and 3 mg of risperidone. Fasting morning blood samples were analyzed for PRL, and the occurrence of hyper-prolactinemic symptoms in the patients was evaluated.
Results: Elevated PRL levels were found in 16 (89%) of the patients receiving risperidone and in 7 (24%) of the patients receiving olanzapine, but in none of the patients receiving clozapine. In addition, there was a significant difference in median PRL level among the treatment groups (p < .0001), in that the PRL level was higher both in the patients treated with risperidone and in the patients treated with olanzapine, compared to those treated with clozapine. Moreover, hyperpro-lactinemic symptoms-menstrual disturbances, galactorrhea, impotence, oligospermia, and decreased libido-were reported in 8 (44%) of the risperidone-treated patients and in 1 (3%) of the olanzapine-treated patients, but in none of the clozapine-treated patients.
Conclusion: Treatment with risperidone was frequently associated with hyperprolactinemia and related symptoms, whereas the occurrence of PRL elevation and related symptoms was modest in patients receiving olanzapine and nonexistent in those receiving clozapine. Thus, atypical anti-psychotics in therapeutic doses differ with regard to effect on PRL secretion.