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Some effects of risperidone and quetiapine on growth parameters and hormone levels in young pigtail macaques
Gene Sackett1, Alan Unis, Brenda Crouthamel
1Infant Primate Research Laboratory, University of Washington, National Primate Research Center, Seattle, Washington 98195, USA. jsackett@Wanprc.org
Objective:
Atypical antipsychotic drugs are prescribed to young children for a number of symptoms, some with no Food and Drug Administration approval for children. Effects on growth of children have received little experimental study. We assessed the effects of two atypicals, risperidone and quetiapine, on growth, prolactin, and thyroid hormones of young pigtail macaques (macaca nemestrina), modeling potential effects on 4-8-year-old children.
Methods:
Subjects were studied blindly after random assignment to risperidone (N = 10), quetiapine (N = 10), or placebo (N = 20). Four phases were studied: (1) predrug, 9-12 months of age; (2) low dose (risperidone 0.025 mg/kg, quetiapine 2 mg/kg), 13-16 months; (3) high dose (risperidone 0.05 mg/kg, quetiapine 4 mg/kg), 17-20 months; (4) postdrug, 21-24 months. Body weight was measured daily, skeletal dimension monthly, and bone mineralization and hormones bimonthly.
Results:
Our primary result showed that, compared with placebo, neither drug had detrimental effects on body weight, skeletal dimensions, or thyroid hormones. However, in a transient effect, bone density was lower following low-dose risperidone than either quetiapine or placebo. In both drug phases, risperidone prolactin was higher than the other groups, which did not differ. The higher prolactin of the risperidone group may partially explain the bone density effect.
Conclusion:
This 16-month study of young, developing pigtail macaques given risperidone at doses from 0.025 to 0.05 mg/kg or quetiapine at doses from 2 to 4 mg/kg suggests that these drugs are safe for normal body weight and skeletal growth in young pigtail macaques given an adequate diet, although these drugs are known to cause significant weight gain and other metabolic changes in some children, adolescents, and adult humans. In addition, the results, although transient in our study, also suggest that research in children on bone mineralization effects of risperidone, and possibly other antipsychotic drugs, may be warranted.
