Effects of Short- and Long-Term Risperidone Treatment on Prolactin Levels in Children with Autism

Background: The effects of short- and long-term risperidone treatment on serum prolactin were assessed in children and adolescents with autism. Methods: Patients with autism (N = 101, 5-17 years of age) were randomized to an 8-week trial of risperidone or placebo and 63 then took part in a 4-month open-label follow-up phase. Serum samples were obtained at Baseline and Week-8 (N = 78), and at 6-month (N = 43) and 22-month (N = 30) follow-up. Serum prolactin was determined by immunoradiometric assay; dopamine type-2 receptor (DRD2) polymorphisms were genotyped. Results: Baseline prolactin levels were similar in the risperidone (N = 42) and placebo (N = 36) groups (9.3 ± 7.5 and 9.3 ± 7.6 ng/ml, respectively). After 8 weeks of risperidone, prolactin increased to 39.0 ± 19.2 ng/ml, compared with 10.1 ± 8.8 ng/ml for placebo (p < .0001). Prolactin levels were also significantly increased at 6 months (32.4 ± 17.8 ng/ml; N = 43, p < .0001) and at 22 months (N = 30, 25.3 ± 15.6 ng/ml, p < .0001). Prolactin levels were not associated with adverse effects and DRD2 alleles (Taq1A, -141C Ins/Del, C957T) did not significantly influence baseline levels or risperidone-induced increases in prolactin. Conclusions: Risperidone treatment was associated with two- to four-fold mean increases in serum prolactin in children with autism. Although risperidone-induced increases tended to diminish with time, further research on the consequences of long-term prolactin elevations in children and adolescents is needed.