Approximately one in six adults reports having “overactive bladder” symptoms such as urgency, urge incontinence, frequency, or nocturia. The prevalence of these symptoms increases with age. Pharmacologic treatment of overactive bladder symptoms is based on the use of anticholinergic drugs that block the parasympathetic pathways and reduce detrusor muscle contraction. The effectiveness of these drugs remains uncertain and they have significant side effects (e.g., dry mouth, constipation, headache). Herbison and colleagues conducted a systematic review of anticholinergic therapy for overactive bladder symptoms.

The authors used the Cochrane Incontinence Group's register of controlled trials plus a search of citations to identify all randomized controlled trials of overactive bladder or detrusor overactivity that compared an anticholinergic drug with placebo. Of the 64 potential trials, 32 trials with 6,800 participants met inclusion criteria for the analysis. The sample sizes ranged from 20 to 1,529 (median, 155) and involved more than twice as many women as men, although some trials did not report sex. Six drugs were studied, and the trials differed in inclusion criteria, methodology, duration of follow-up, and outcome measures.

Patients taking an anticholinergic agent were more likely to report subjective improvement than patients taking placebo—equivalent to about one less leakage episode or one micturition fewer per 48-hour period. Anticholinergic agents also were consistently associated with improvements in measures of bladder capacity. Maximum cystometric capacity increased by an average 49 mL and average volume at first contraction increased by 52 mL. Average residual volume was 4 mL greater in the drug-treated patients, but significant heterogeneity was observed. Drug and placebo groups did not differ significantly in withdrawals because of adverse events, but dry mouth was two and one half times as common in patients treated with an anticholinergic agent in the 20 trials reporting side effects.

The authors conclude that therapy with an anticholinergic agent results in small improvements in symptoms and urodynamic measures when compared with placebo but is associated with significant side effects, especially dry mouth. They note that improvements were reported in both treatment and placebo groups, but few studies used recognized quality-of-life measures. They question the clinical significance of the improvements reported with anticholinergic agents and call for direct comparisons of these medications with bladder retraining and other nonpharmacologic treatments for overactive bladder symptoms.