Is it time for a new choice of treatments for underactive bladder?

A range of mechanisms and systems underly urinary bladder contractions. However, when contraction is inhibited, such as with underactive bladder (UAB), it is not always clear which mechanism is at fault. Parasympathomimetics (muscarinic agonists and acetylcholinesterase inhibitors) might be beneficial for enhancing contractions of the bladder, which is of particular interest in the pharmaceutical treatment of UAB. This study systematically reviewed and meta-analysed the current literature to assess the effectiveness of parasympathomimetics for the treatment of underactive bladder. An a priori protocol was registered in PROSPERO. Database searches were undertaken within Embase, PubMed and CENTRAL and included randomised and non-randomised controlled trials that incorporated patients with UAB. Articles that compared any parasympathomimetic medication to a placebo, no treatment, or other pharmaceuticals were included. A total of 3024 participants were included across twelve trials. There were significant differences between selected comparators and parasympathomimetics (favouring parasympathomimetics) in the number of patients with urinary retention, although no overall difference was identified to mean postvoid volume. There was a significant difference at up to 1-week post‐intervention, favouring parasympathomimetics, but no difference at 1-month post‐intervention. There were no differences identified in adverse events. The overall evidence is of low quality, and studies tended to end without long-term follow-ups. However, there are some observed benefits, with no major identified risk factors from parasympathomimetic prescriptions. Although it is not entirely possible to draw clear evidence‐based conclusions from the current literature, this study has identified a clear need for well‐controlled clinical trials to be conducted in the future.