Prospective Pilot Study of Mirabegron in Pediatric Patients with Overactive Bladder.

Background: Antimuscarinics are the pharmacologic mainstay of overactive bladder (OAB) management, but side effects limit their use. Mirabegron, a new molecule with a distinct mechanism of action (β3-adrenoreceptor agonist), was recently approved as monotherapy for idiopathic OAB in adults but has not been studied in the pediatric population.

Objective: To evaluate the efficacy and safety of mirabegron to treat urinary incontinence in children with idiopathic OAB who were refractory to and/or intolerant of antimuscarinics.

Design, Setting, And Participants: A prospective off-label study using mirabegron was conducted. Pediatric patients without symptom improvement under behavioral and medical therapies and/or with significant side effects with at least two different antimuscarinic agents were recruited.

Outcome Measurements And Statistical Analysis: Our primary outcome was better reported efficacy than with the use of prior anticholinergic medication. Secondary end points were tolerability, safety, and satisfaction. Efficacy and tolerability were assessed with voiding diaries, postvoid residuals, urine cultures, electrocardiogram, and vital signs. Families were questioned for continence, side effects, compliance, and Patient Perception of Bladder Condition (PPBC) questionnaire. The Wilcoxon rank sum test and Wilcoxon signed rank test were used for statistical analysis.

Results And Limitations: A total of 58 patients were recruited at a median age of 10.1 yr and were on mirabegron for a median of 11.5 mo. Median bladder capacity improved from 150ml to 200ml (p<0.001). Continence improved in 52 of 58, with 13 being completely dry. Median PPBC improved from 4.0 to 2.0 (p<0.001). Eight patients reported mild or moderate side effects. Absence of a placebo group is a limitation of the study.

Conclusions: Mirabegron, a novel first-in-class therapy, appeared as a safe and effective alternative for children with idiopathic OAB refractory to antimuscarinics.

Patient Summary: We evaluated the efficacy and safety of mirabegron to treat incontinence in pediatric patients. Continence, median voided volumes, and quality of life were improved after the introduction of mirabegron, and few side effects were reported.