Overactive bladder drugs and constipation: a meta-analysis of randomized, placebo-controlled trials

Anticholinergic drugs are commonly prescribed for symptomatic treatment of overactive bladder (OAB). While recent meta-analyses have characterized the prevalence of dry mouth among patients utilizing OAB medications, prevalence of constipation has not been systematically reviewed.

To provide an effect measure for constipation associated with anticholinergic OAB drugs versus placebo.

A meta-analysis of trials with darifenacin, fesoterodine, oxybutynin, solifenacin, tolterodine, and trospium was conducted. All randomized, placebo-controlled studies of anticholinergic OAB drugs published in English language and identified in Medline and Cochrane databases were considered for inclusion in this meta-analysis. Those meeting predetermined design characteristics and having sufficient duration (≥2 weeks) were included. Constipation-related data from all included studies were abstracted.

One hundred two English-language, randomized, placebo-controlled trials were originally identified. Thirty-seven studies were ultimately included in the analysis, involving 19,434 total subjects (12,368 treatment+7,066 placebo patients). The odds ratios for constipation compared with placebo were as follows: overall [odds ratio (OR) 2.18, 95% confidence interval (CI)=1.82-2.60], tolterodine (OR 1.36, 95% CI=1.01-1.85), darifenacin (OR 1.93, 95% CI=1.40-2.66), fesoterodine (OR 2.07, 95% CI=1.28-3.35), oxybutynin (OR 2.34, 95% CI=1.31-4.16), trospium (OR 2.93, 95% CI=2.00-4.28), and solifenacin (OR 3.02, 95% CI=2.37-3.84).

Our results demonstrate that patients prescribed anticholinergic OAB drugs are significantly more likely to experience constipation. Differences in muscarinic receptor affinities among individual agents may possibly account for the modest variation in constipation rates observed; however, such a determination warrants additional research.