The effect of smoking status on the plasma concentration of prolactin already elevated by risperidone treatment in schizophrenia patients

Smoking prevalence for schizophrenic patients is higher than for the general population. Inter-individual variability in hyperprolactinemia induced antipsychotics particularly risperidone can be explained by smoking status to some extent. We therefore studied the effects of smoking status on the plasma concentration of prolactin. Subjects included 154 schizophrenia patients (61 males, 93 females) who had received 3 mg of risperidone twice daily for at least 4 weeks. Sample collections were conducted 12 h after the bedtime dosing. The plasma concentrations of prolactin in the females were significantly higher than in the males (117.6 +/- 69.3 ng/ml vs. 52.9 +/- 30.7 ng/ml, p<0.001). The mean (+/-SD) plasma concentrations of prolactin did not differ between smokers and nonsmokers in the males (59.5 +/- 31.2 ng/ml vs. 47.6 +/- 29.3 ng/ml, not significant (ns)), but there was a significant difference in the females (100.2 +/- 59.1 vs. 134.0 +/- 74.6, ng/ml, p<0.05). Multiple regression analyses including gender, plasma drug concentration and age revealed that the plasma concentration of prolactin positively correlated with gender (standardized beta = 0.452, p<0.001) and negatively with age (standardized beta = -0.171, p<0.05) and smoking status (standardized beta = -0.232, p<0.01). These findings suggest that smoking status has an impact on prolactin concentration during risperidone treatment. However, further study is required to determine whether these findings have clinical implications. (C) 2011 Elsevier Inc. All rights reserved.