The article you requested is

A Crossover Study of Prolactin Changes Associated With Risperidone and Olanzapine

J Clin Psychiatry 2006;67(9):1470-1471 [letter]

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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