Differences in plasma prolactin levels in patients with schizophrenia treated on monotherapy with five second-generation antipsychotics.

Although second-generation antipsychotics (SGAs) are characterized by fewer prolactin (PRL)-related side effects compared with first-generation antipsychotics, the detailed effects of SGAs on the plasma PRL levels still remain unclear. We examined the differences in plasma PRL levels among 268 patients treated for schizophrenia with olanzapine (OLZ), risperidone (RIS), aripiprazole (ARP), quetiapine (QTP), or perospirone (PER). The participants had received antipsychotic monotherapy with stable doses of OLZ, RIS, ARP, QTP, or PER for ≥ 3 weeks, and fasting blood samples were drawn to examine plasma PRL levels. The differences in median plasma PRL levels in all (P<0.001), male (P<0.001) and female patients (P<0.001) among the five SGA groups were statistically significant. A stepwise multiple regression analysis showed that ARP treatment was found to contribute to lower plasma PRL level, while female sex, RIS, OLZ and chlorpromazine equivalent dose were found to contribute to a higher plasma PRL level. The median value of plasma PRL level in the RIS group was twice as much compared with that in the OLZ group, although this was not statistically significant. In this study, OLZ had a considerable effect on plasma PRL level, similar to RIS, while PER did not affect plasma PRL levels, similar to QTP. Further studies are needed to clarify the differences in plasma PRL levels among SGAs.