Add-on mirabegron safe for treating paediatric overactive bladder
Therapy regimens with add-on mirabegron may be safely used in children with refractory overactive bladder, according to data from a prospective off-label study.
A total of 35 overactive bladder paediatric patients (median age 10.3 years) received treatment with add-on mirabegron. All patients did not present symptom improvement under intensive behavioural and medical therapies and/or had significant side effects on antimuscarinic dose escalation.
The primary endpoint was better-reported efficacy compared with the use of prior antimuscarinic monotherapy. Secondary endpoints were tolerability, safety and satisfaction.
Efficacy and tolerability were evaluated using voiding diaries, post-void residuals (PVR), urine cultures, ECG and vital signs. Families were interviewed for continence, side effects and compliance. Statistical analysis was performed using Wilcoxon signed rank test.
Following treatment with add-on mirabegron for a median of 16.4 months, median bladder capacity improved from 50 percent to 74 percent expected bladder capacity (p<0.001).
Furthermore, continence improved in all patients, and 12 patients were reported to be completely dry.
On the other hand, two patients had an increase in post-void residual, and one developed urinary tract infection. Side effects, which were mild to moderate in severity, were reported in seven patients.
There were two cases of treatment discontinuation, one due to side effects and another to post-void residual.
These data highlight the potential of add-on mirabegron in the treatment of refractory overactive bladder, with the drug being safe and well-tolerated in children.
Mirabegron, a β3-adrenoreceptor agonist, has been shown to improve the storage capacity of the bladder, without impairing bladder contraction during voiding. The agent is rapidly absorbed after oral administration and is metabolized in the liver via multiple pathways. Caution must be exercised when using mirabegron in patients receiving ketoconozole or other potent CYP3A inhibitors as mirabegron may be subject to clinically relevant drug–drug interactions. [Neurourol Urodyn 2014;33:17–30]