Gender, age, smoking behaviour and plasma clozapine concentrations in 193 Chinese inpatients with schizophrenia.

摘要

AIM: To study the relationship between age, gender, cigarette smoking and plasma concentrations of clozapine (CLZ) and its metabolite, norclozapine (NCLZ) in Chinese patients with schizophrenia. METHODS: Data from a therapeutic drug monitoring programme were analysed retrospectively. One hundred and ninety-three Chinese inpatients with schizophrenia were assessed using clinical data forms. Steady-state plasma concentrations of CLZ and NCLZ were assayed using high-performance liquid chromatography. Comparisons of dosage and plasma CLZ concentrations were undertaken between males (n = 116) and females (n = 77), younger (40 years, n = 111) and current male smokers (n = 50) and nonsmokers (n = 66). RESULTS: (i) Plasma CLZ concentrations demonstrated large interindividual variability, up to eightfold at a given dose; (ii) there were significant effects of gender on plasma CLZ concentrations (relative to dose per kg of body weight) with female patients having significantly higher concentrations than males (30.09 +/- 24.86 vs. 19.87 +/- 3.55 ng ml(-1) mg(-1) day(-1) kg(-1); P < 0.001); (iii) there were no significant differences in plasma CLZ concentrations between those patients 40 years; and (iv) there were no significant differences in plasma CLZ concentrations between male smokers and nonsmokers, despite the CLZ dosage for smokers being significantly higher. CONCLUSIONS: Plasma CLZ concentrations vary up to eightfold in Chinese patients. Among the patient-related factors investigated, only gender was significant in affecting CLZ concentrations in Chinese patients with schizophrenia, with female patients having higher levels.