Background: Risperidone (RIS) has the highest propensity to elevate plasma prolactin (PRL) levels. While the active metabolite 9-hydroxy-risperidone (9-OH-RIS) plays a predominant role in the efficacy and side effects of RIS, the mechanistic details are still poorly understood. The present study evaluated the gender differences in the relationship between plasma levels of RIS or 9-OH-RIS and PRL.
Methods: Twenty-one male and 19 female subjects treated with RIS were enrolled in the present series. All patients had been receiving RIS for at least 4 weeks at an average dosage of 4.7 mg/day. Plasma RIS, 9-OH-RIS and PRL levels were measured.
Results: In the male patients, there was no correlation between the RIS dosage and plasma PRL levels, between plasma RIS levels and PRL levels, or between the plasma 9-OH-RIS levels and PRL levels. In the female patients, there was a significant positive correlation between the plasma 9-OH-RIS levels and PRL levels (rs=0.456, p=0.049). There was a trend toward a significant positive correlation between the RIS dosage and plasma PRL levels. There was no correlation between the plasma RIS levels and PRL levels.
Conclusion: 9-OH-RIS is considered to play a more important role in PRL elevation than RIS, and a gender difference exists in the effect of 9-OH-RIS on PRL level.
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