The effect of psychotropic medications on the occurrence of constipation in hospitalized psychiatric patients.

To the Editors: Constipation is a common problem in psychiatric patients, with a reported 2-year period prevalence of 36.3% in a population of patients with schizophrenia using antipsychotics and a 4-year period prevalence of 57.7% in a population of patients with a mood disorder. The impact of constipation on the quality of life can be compared with that of other medical conditions, such as diabetes, depression, and hypertension. Furthermore, constipation can lead to severe complications such as fecal impaction, bowel perforation, and death. Many conditions like several mental disorders; psychotropic drugs including antipsychotics, antidepressants (especially tricyclic antidepressants), and mood stabilizers; prevalent comorbidities such as hypothyroidism and diabetes; and common unhealthy lifestyle factors such as poor diet and inactivity, have all been associated with an increased risk of developing constipation. Despite the high prevalence of constipation in psychiatric patients, the incidence and risk factors of constipation in this vulnerable group of patients have hardly been studied. Therefore, the aim of the study was to estimate the risk of psychotropic medication use on new-onset constipation in patients with severe mental illness (SMI). A retrospective cohort study was performed in a psychiatric center in The Netherlands. Patients with a psychiatric disorder hospitalized for at least 1 month in the period of 2007Y2010 were included in the study. Information about diagnosis, duration of hospitalization and medication prescriptions was obtained from the Electronic Healthcare Information System and the Pharmacotherapeutical Response and Inventory Management System. Diagnoses were made according to theDiagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria by medical staff. Patients receiving at least one prescription of psychotropic medication during their hospitalization were considered as users of this psychotropic medication, and all psychotropic medications were classified according to Anatomical Therapeutic Chemical classification system code. Laxative use was used as a proxy measure for constipation, and patients receiving at least one prescription of laxative medication during their hospitalization were considered cases. Patients with a prescription for a laxative during the first month of hospitalization were excluded because the focus of this study was on new-onset constipation. The following potential confounders were taken into account based on the current literature: sex, age, duration of medication use, a diagnosis for depression, a diagnosis for a cognitive disorder, the use of diuretics, calcium channel blockers, motility inhibitors, anti-Parkinson drugs, hypnotics, antispasmodics, antiepileptics, sympathicomimetics, antidiarrheal drugs, calcium supplements, iron supplements, antihistamines, opioids, nonsteroidal anti-inflammatory drugs, and other psychotropics and comorbid disorders including diabetes, hypothyroidism, and acromegaly. The use of antidiabetic medication, antigrowth hormones, and thyroid hormones were used as proxy measures for diabetes, acromegaly, and hypothyroidism, respectively. Cox proportional hazards regression association models were used to evaluate the risks of psychotropic medications and age on incident constipation. All potential confounders were entered as covariates in all models. Each covariate that influenced the hazard ratio by more than 10%was included in the final Cox regression analysis. All covariates were assumed to be time independent. In addition, all analyses were checked for multicollinearity. Interaction tests were performed between antidepressants, antipsychotics, and mood stabilizers, as these agents are also considered secondary causes of constipation. All data analyses were performed using SPSS version 18. A total of 3176 patients were eligible for inclusion in the study. The mean T SD age of the patients was 46.7 T 18 years; 49.9% were men. Of all patients, 25.9%, Journal of Clinical Psychopharmacology & Volume 33, Number 4, August 2013 Letters to the Editors