METHODS: The protocol was registered in PROSPERO, and searches undertaken in PubMed, Embase, and CENTRAL, including randomized and non-randomized controlled trials of patients with underactive bladder, comparing parasympathomimetic to placebo, no treatment, or other pharmaceuticals. Risk ratios, odds ratios, and mean differences were calculated.
RESULTS: Twelve trials with 3024 participants were included. There was a significant difference between parasympathomimetics and comparators (favoring parasympathomimetics) in the number of patients with urinary retention (risk ratio 0.55, 95% confidence interval [CI] 0.3-0.98, p = 0.04, low quality of evidence). There was no difference in mean postvoid volume overall (MD -41.4 ml, 95% CI -92.0 to 9.1, p = 0.11, low quality of evidence). There was a significant difference at up to 1 week post-intervention, favoring parasympathomimetics (MD -77.5 ml, 95% CI -90.9 to -64.1, p < 0.001, low quality of evidence), but no difference at 1 month post-intervention. There was no difference in adverse events (odds ratio 1.19, 95% CI 0.62-2.28, p = 0.6, moderate quality of evidence).
CONCLUSIONS: The evidence supporting the use of parasympathomimetics is of low quality, with relatively short follow-up durations. Overall, it is not possible to draw clear evidence-based conclusions from the current literature, presenting the use of parasympathomimetics for treating underactive bladder as a key area that requires future well-controlled clinical trials.