Nocturnal enuresis in patients taking clozapine, risperidone, olanzapine and quetiapine: comparative cohort study

Background Nocturnal enuresis has been reported in patients taking clozapine, but the incidence has not been accurately established. The incidence of enuresis in patients taking risperidone, olanzapine or quetiapine is unknown. Aims To compare nocturnal enuresis in patients taking clozapine with that in patients taking risperidone, olanzapine or quetiapine. Method Observational cohort study using prescription event monitoring methods. Patients prescribed atypical antipsychotic medicines were followed up by questionnaires that were sent to their medical practitioner. Practitioners were asked to directly ask their patients about bed-wetting. Results Nocturnal enuresis was reported by 17 of 82 (20.7%) patients taking clozapine, 11 of 115 (9.6%) taking olanzapine, 7 of 105 (6.7%) taking quetiapine and 12 of 195 (6.2%) taking risperidone. Compared with clozapine, the risk of nocturnal enuresis was significantly lower in patients taking olanzapine (odds ratio, OR=0.43, 95% CI 0.19-0.96), quetiapine (OR=0.33, 95% CI 0.13-0.59) or risperidone (OR=0.27, 0.12-0.59), with odds ratios adjusted for age, gender and duration of treatment. Conclusions Approximately one in five patients prescribed clozapine experienced bed-wetting. This was significantly higher than the rate of nocturnal enuresis in patients taking olanzapine, quetiapine or risperidone.