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. 2015 Oct;5(5):256-62.
doi: 10.1177/2045125315591917.

Factors predicting use of laxatives in outpatients stabilized on clozapine

Loren Bailey  1 , Seema Varma  2 , Nina Ahmad  3 , Siobhan Gee  1 , David M Taylor  4
Affiliations

Factors predicting use of laxatives in outpatients stabilized on clozapine

Loren Bailey et al. Ther Adv Psychopharmacol. 2015 Oct.

Abstract

Constipation is a common and sometimes fatal side effect of clozapine treatment. In this study, we aimed to identify factors associated with clozapine-induced constipation. Data on 202 outpatients stabilized on clozapine treatment were collected. Of these, 71 patients (35%) had a current prescription for laxatives (a proxy for the presence of constipation). Mean clozapine dose was 400.4 mg/day in those prescribed laxatives and 390.1 mg/day in those not prescribed laxatives (p = 0.67), while mean clozapine plasma concentration was 0.53 mg/l and 0.49 mg/l, respectively (p = 0.29). Patients using laxatives had on average 29% higher norclozapine concentrations (mean = 0.34 mg/l) than those who did not use laxatives (mean = 0.27 mg/l; p = 0.046). Laxative use was more common in female patients (49.1%) than male patients (29.1%; p < 0.01). Prescribers should be vigilant for constipation at any dose or plasma concentration of clozapine and should be mindful that male patients may be undertreated. Norclozapine concentrations may predict clozapine-induced constipation.

Keywords: N-desmethylclozapine; clozapine; constipation; laxatives.

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Conflict of interest statement

Conflict of interest statement: D.T. has received payments for lectures and advisory boards from Eli Lilly, Lundbeck, BristolMyersSquibb, AstraZeneca, Sunovion and Otsuka. S.G. has received payments for lectures and advisory boards from Sunovion. The other authors declare no conflicts of interest in preparing this article.

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