A Crossover Study of Prolactin Changes Associated With Risperidone and Olanzapine

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Sir: We read with interest the recent article by Melkersson¹ that described the differential effect on prolactin elevation in schizophrenic patients treated with clozapine (none of the patients had elevated prolactin), olanzapine (24% of the patients had elevated prolactin), and risperidone (89% of the patients had elevated prolactin). Previous head-to-head clinical trials have revealed similar results.^2-5 However, these comparison studies might be limited by the individual variation in endocrine profiles, demographic variables such as age and gender, and concomitant medication use.^6,7‘ ‹