Effects Of Dose, Age, Sex, Body Weight, And Smoking On Plasma Concentrations Of Olanzapine And N-Desmethyl Olanzapine In Inpatients With Schizophrenia

PurposeThis study aimed to investigate the combined effects of dose, age, sex, body weight, and smoking on plasma concentrations of olanzapine (OLA) and N-desmethyl olanzapine (DMO) in Chinese inpatients with schizophrenia. MethodsA retrospective study including 185 inpatients was conducted. The steady-state plasma concentrations of OLA (C-OLA) and DMO (C-DMO) were measured using high-performance liquid chromatography-tandem mass spectrometry. The combined effects of dose, age, sex, body weight, and smoking on C-OLA and C-DMO were evaluated. FindingsMultiple linear regression analyses revealed that dose, age, body weight, and smoking had significant effects on C-OLA and C-DMO in inpatients with schizophrenia treated with OLA. The dose was the most important determinant of C-OLA and C-DMO and was positively correlated with both. Furthermore, smokers exhibited a significantly lower C-OLA and COLA + DMO, whereas higher body weight led to the reduction of C-OLA, C-DMO, and COLA + DMO. Advanced age was associated with lower C-DMO. ImplicationsThese results suggest that dose, age, body weight, and smoking have a significant influence on the plasma concentration of OLA and its metabolite DMO. Clinicians should consider the combined effects when prescribing OLA to patients with schizophrenia.