Is Myrbetriq (mirabegron) effective for treating overactive bladder symptoms in patients with neurogenic bladder?

Mirabegron (Myrbetriq) for Neurogenic Bladder

Mirabegron is FDA-approved and effective for treating neurogenic detrusor overactivity (NDO) in pediatric patients aged 3 years and older weighing 35 kg or more, demonstrating significant improvements in bladder capacity, detrusor pressure, and continence rates. 1

FDA-Approved Indication

Mirabegron extended-release tablets are specifically indicated for neurogenic detrusor overactivity in pediatric patients aged 3 years and older weighing ≥35 kg, representing a distinct FDA-approved use beyond non-neurogenic overactive bladder. 1 This approval distinguishes mirabegron from the guidelines for non-neurogenic OAB, which explicitly exclude neurogenic bladder populations. 2

Dosing for Neurogenic Bladder

For pediatric patients with NDO weighing ≥35 kg:

• Start with 25 mg orally once daily with food 1
• After 4-8 weeks, may increase to 50 mg once daily if inadequate symptom control 1
• Tablets must be swallowed whole with water; do not chew, divide, or crush 1

Clinical Efficacy in Neurogenic Bladder

The evidence demonstrates robust improvements in neurogenic bladder patients:

Urodynamic Parameters:

• Maximum cystometric capacity increased by 125 mL (from 322 to 446 mL, p<0.0001) 3
• End-filling detrusor pressure decreased by 12 cm H₂O (from 44 to 31 cm H₂O, p<0.0001) 3
• Intensity of detrusor overactivity contractions reduced by 20 cm H₂O 3

Clinical Outcomes:

• 72% of incontinent patients achieved dryness after initiating mirabegron 3
• Effective as adjuvant therapy in patients refractory to oxybutynin and/or onabotulinumtoxinA 3

Safety Monitoring Requirements

Blood Pressure Monitoring:

• Monitor blood pressure periodically, especially during initial treatment 4, 1
• Mirabegron can cause dose-dependent blood pressure increases 4
• Not recommended in severe uncontrolled hypertension 1

Urinary Retention Risk:

• Administer with caution in patients with bladder outlet obstruction due to risk of urinary retention 1
• Monitor post-void residual volume regularly, particularly in patients with lower urinary tract symptoms 4
• Advise patients to discontinue if worsening voiding symptoms or urinary stream occurs 5

Pediatric-Specific Monitoring:

• Blood pressure and transaminases showed no significant adverse changes in pediatric neurogenic bladder patients 3
• No adverse effects were reported in the pediatric neurogenic bladder cohort 3

Common Adverse Events in Neurogenic Bladder

The most commonly reported adverse reactions in pediatric patients with NDO (≥3%) include:

• Urinary tract infection 1
• Nasopharyngitis 1
• Constipation 1
• Headache 1

Key Clinical Considerations

Combination Therapy Potential:

• Mirabegron proved effective as adjuvant treatment in patients already refractory to antimuscarinics (oxybutynin) and/or onabotulinumtoxinA 3
• This suggests utility in combination regimens for difficult-to-treat neurogenic bladder cases 3

Mechanism Advantage:

• Mirabegron targets β3-adrenoreceptors, improving bladder storage without altering void contractions 6
• This distinct mechanism offers advantages over antimuscarinics, particularly avoiding anticholinergic side effects like dry mouth, constipation, and cognitive effects 7, 6

Critical Pitfalls to Avoid

• Do not substitute mirabegron extended-release tablets with mirabegron granules on a milligram-per-milligram basis—these are different products 1
• Do not crush or chew tablets, as this destroys the extended-release formulation 1
• Do not overlook hypersensitivity contraindications, including risk of angioedema of face, lips, tongue, and/or larynx 1
• Do not use in patients with severe uncontrolled hypertension 1