Background: This analysis was designed to investigate prolactin levels in children and adolescents on long-term risperidone treatment and explore any relationship with side effects hypothetically attributable to prolactin (SHAP). Method: Data from 5 clinical trials (total N= 700) were pooled for this post hoc analysis. Children and adolescents aged 5 to 15 years with subaverage intelligence quotients and conduct or other disruptive behavior disorders received risperidone treatment (0.02–0.06 mg/kg/day) for up to 55 weeks. Outcome measures analyzed included serum prolactin levels, reported adverse events, and the conduct problem subscore of the Nisonger Child Behavior Rating Form. Results: Mean prolactin levels rose from 7.8 ng/mL at baseline to a peak of 29.4 ng/mL at weeks 4 to 7 of active treatment, then progressively decreased to 16.1 ng/mL at weeks 40 to 48 (N= 358) and 13.0 ng/mL at weeks 52 to 55 (N= 42). There was no relationship between prolactin levels and age. Females returned to a mean value within the normal range (≤ 30 ng/mL) by weeks 8 to 12, and males were close to normal values (≤ 18 ng/mL) by weeks 16 to 24. At least 1 SHAP was reported by 13 (2.2%) of 592 children. There was no direct correlation between prolactin elevation and SHAP.

Conclusion: With long-term risperidone treatment in children and adolescents, serum prolactin levels tended to rise and peak within the first 1 to 2 months and then steadily decline to values within or very close to the normal range by 3 to 5 months.