Is Myrbetriq (mirabegron) safe for a 14-year-old with overactive bladder?

Safety of Mirabegron (Myrbetriq) for a 14-Year-Old with Overactive Bladder

Mirabegron is FDA-approved for pediatric patients aged 3 years and older with neurogenic detrusor overactivity (NDO), but its use in adolescents with idiopathic overactive bladder would be off-label and should be considered only after failure of first-line treatments. 1, 2

FDA Approval Status and Dosing for Pediatric Patients

• Mirabegron received FDA approval for pediatric patients aged 3 years and older with neurogenic detrusor overactivity (NDO) in March 2021 2
• For pediatric patients weighing ≥35 kg, the recommended starting dose is 25 mg once daily, which may be increased to 50 mg once daily after 4-8 weeks 1
• The extended-release tablets should be swallowed whole with water and taken with food in pediatric patients 1

Efficacy in Pediatric Populations

• A prospective pilot study of mirabegron in pediatric patients with overactive bladder who were refractory to and/or intolerant of antimuscarinics showed promising results 3
• In this study of 58 pediatric patients (median age 10.1 years), continence improved in 52 of 58 patients, with 13 becoming completely dry 3
• Median bladder capacity improved from 150 ml to 200 ml (p<0.001) 3

Treatment Algorithm for Overactive Bladder in Adolescents

1. First-line therapy: Behavioral interventions (bladder training, pelvic floor exercises, fluid management) 4, 5
2. Second-line therapy:
   • Antimuscarinic medications (if no contraindications) 6
   • Consider mirabegron if antimuscarinics are ineffective or poorly tolerated 7, 3
3. Third-line therapy: Specialist referral for refractory cases 6

Safety Considerations for Mirabegron in Adolescents

• Mirabegron has a more favorable side effect profile compared to antimuscarinic agents, with fewer anticholinergic effects such as dry mouth, constipation, and cognitive impairment 7, 8
• Common adverse reactions in pediatric patients with NDO (≥3%) include urinary tract infection, nasopharyngitis, constipation, and headache 1
• In the pediatric pilot study, only 8 of 58 patients reported mild to moderate side effects 3

Monitoring Recommendations

• Blood pressure should be periodically monitored, as mirabegron can increase blood pressure 1
• Mirabegron is not recommended in patients with severe uncontrolled hypertension 1
• Monitor for signs of urinary retention, especially if used with antimuscarinic drugs 1
• Watch for potential drug interactions, particularly with medications metabolized by CYP2D6 1

Cautions and Contraindications

• Contraindicated in patients with hypersensitivity to mirabegron or any inactive ingredients 1
• Use with caution in patients with bladder outlet obstruction due to risk of urinary retention 1
• Angioedema of the face, lips, tongue, and/or larynx has been reported with mirabegron 1

Summary

While mirabegron has FDA approval for pediatric patients with neurogenic detrusor overactivity, its use for idiopathic overactive bladder in a 14-year-old would be off-label. However, evidence suggests it may be a safe and effective option, particularly for adolescents who have failed or cannot tolerate antimuscarinic medications. Close monitoring for adverse effects, particularly blood pressure changes, is essential.