Efficacy and safety of Mirabegron as adjuvant treatment in children with refractory neurogenic bladder dysfunction

When patients with neurogenic bladder become refractory, there are different alternatives, such as the use of β3-adreceptor agonists. The aim of the present study is to evaluate efficacy and safety of Mirabegron as adjuvant treatment.

37 patients under 18 years of age who underwent Mirabegron were retrospectively studied. The inclusion criteria were: cases with neurogenic bladder who were under clean intermittent catheterization (CIC) programs and refractory to oral oxybutynin (Group A) and/or onabotulinumtoxinA (Group B). Once refractory neurogenic bladder was confirmed by clinical and/or urodynamic studies, Mirabegron 25 mg/day was indicated and evaluation was performed in the third month without stopping therapy. Systolic/diastolic blood pressure and transaminases were monitored. Paired t test and Pearson's chi - squared test were used.

Maximum cystometric capacity increased significantly by 125 mL, from 322 to 446 ml (p < 0.0001). End-filling detrusor pressure decreased significantly by 12 cm H₂O, from 44 to 31 cm H₂O (p < 0.0001). The variation in both parameters was significant in Groups A and B. The presence of detrusor overactivity increased globally from 21 to 32% after starting Mirabegron, but the intensity of contractions was reduced in 20 cm H₂O. Of the 18 patients who were incontinent before, 13 cases (72%) remained dry after initiating therapy with Mirabegron. None of the patients stated having suffered any adverse effects. Blood pressure and transaminases showed no significant difference. None of the patients discontinued treatment due to intolerance to Mirabegron (Summary Table).

In our study the treatment with Mirabegron improved significantly the clinical and urodynamic parameters. A significant increase in bladder capacity and a significant decrease in end-filling detrusor pressure were observed in both groups. The intensity of overactivity was attenuated. According to the records of the voiding diary, over 70% of the incontinent patients became dry after the administration of Mirabegron. We did not observe any adverse effects. The most important limitations of the present study are its retrospective design, the small size of the sample population and of each group, and the use of only one dose of Mirabegron.

Mirabegron as adjuvant treatment in children with refractory neurogenic bladder increased bladder capacity, reduced intravesical pressure and helped achieve continence in more than two thirds of the sample population. Mirabegron was safe and well tolerated by children.