Differential olanzapine plasma concentrations by sex in a fixed-dose study

Abstract

This study examined plasma concentrations of olanzapine by sex (20 males and seven females) in an 8-week fixed-dose study. Dosing was 12.5 mg/day for the first week, then 25 mg/day. Trough plasma concentrations were drawn at weeks 1, 3, 5 and 8. Women volunteers were found to have significantly higher plasma concentrations than men. This difference was first evident at study week 5. Women have higher plasma concentrations of olanzapine, possibly due to differences in metabolism of the CYP450 isoenzyme system.