Prevalence and predictors of laxatives use in clozapine-related constipation: an observational study

Clozapine-induced constipation is a frequently overlooked side effect that can prove fatal. This study aimed to investigate the prevalence of constipation and the breakdown of laxatives, and to identify whether use of laxative may be predicted by demographics or baseline metabolic markers in 53 Japanese treatment-resistant schizophrenia inpatients switched to clozapine. Differences of present age, onset age and duration of illness, previous antipsychotic dose using the chlorpromazine equivalent, and 10-items of metabolic markers, including fasting plasma glucose and ratio of triglyceride to high-density lipoprotein cholesterol levels were compared between the laxative and nonlaxative user groups. Sequential changes of defecation scores using Bristol stool form scale, and clozapine dosage at 1, 2 and 3 months were evaluated within each group. Multiple linear stepwise regression analysis was performed to assess the predicting use of laxatives. Half of subjects required treatment with laxative, were significantly older and had longer durations of illness than nonlaxative users. Magnesium oxide and lubiprostone were mainly used singly or in combination. Longer disease duration, and lower levels of fasting blood glucose and insulin resistance were predicting the use of laxatives. Screening and preventive strategies for minimizing clozapine-related constipation should be established in future study.