Some effects of risperidone and quetiapine on growth parameters and hormone levels in young pigtail macaques.

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.