A Prospective Paired Comparison Trial of Mirabegron and Anticholinergics in Patients With Low Bladder Compliance

Low bladder compliance (BC) poses a significant clinical challenge. Nevertheless, studies exploring pharmacological mechanisms to improve BC remain limited. We investigated the efficacy of a β3-adrenoceptor agonist, mirabegron, on BC in comparison with anticholinergics.

This prospective single-arm paired comparison trial included 14 patients with low BC (≤20 mL/cm H2O) despite anticholinergics treatment. After a 2-week anticholinergics-washout period, patients were treated with mirabegron for 8 weeks and then returned to 8 weeks of anticholinergics. Major treatment effect was assessed with urodynamic studies performed at baseline, 8 weeks after mirabegron treatment, and 8 weeks after consecutive anticholinergics treatment (McNemar test, Paired t-test; mean [95% confidence intervals]).

Following mirabegron, 71.43% of patients exhibited a BC of >20 mL/cm H₂O, compared to 54.55% after switching back to anticholinergics (P=0.317). BC improved significantly from 12.02 (9.52-14.52) to 39.67 (21.60-57.73) mL/cm H2O after mirabegron treatment (P=0.007), but subsequently declined to 20.94 (15.78-26.10) mL/cm H₂O after reintroduction of anticholinergics (P=0.075). Maximum cystometric capacity increased from 352.21 (282.78-421.65) to 442.71 (348.95-536.48) mL after mirabegron (P=0.091), but decreased to 402.00 (315.92-488.08) mL after returning to anticholinergics (P=0.218). Notably, detrusor pressure at end-filling decreased significantly with mirabegron, from 30.50 (25.61-35.39) to 14.43 (10.79-18.06) cm H2O (P<0.001), while increasing to 20.36 (16.26-24.46) cm H2O after returning to anticholinergics (P=0.056).

A β3-adrenoceptor agonist, mirabegron, was more effective than anticholinergics in improving BC. Among the two components of improved BC-increased bladder volume and reduced detrusor filling pressure-the β3-adrenoceptor agonist showed a more pronounced effect on lowering detrusor filling pressure, compared to anticholinergics. These findings suggest that β3-adrenoceptor agonists might play an important role in reducing the tension of the bladder wall by controlling detrusor muscle tone, and this may be an important target for future research.