What is the recommended treatment and dosage of mirabegron for overactive bladder symptoms?

Mirabegron Treatment for Overactive Bladder

The recommended treatment for overactive bladder is mirabegron with a starting dose of 25 mg orally once daily, which may be increased to 50 mg once daily after 4-8 weeks if needed and tolerated. 1, 2

Dosage and Administration

• Starting dose: 25 mg orally once daily 1, 2
• Dose adjustment: May increase to 50 mg once daily after 4-8 weeks if needed 1, 2
• Administration:
  • Take tablets whole with water, do not chew, divide, or crush 2
  • Adults can take with or without food 2
  • Pediatric patients should take with food 2

Dose Adjustments for Special Populations

• Severe renal impairment (eGFR 15-29 mL/min/1.73 m²): Do not exceed 25 mg daily 1
• Severe hepatic impairment: Contraindicated 1
• Elderly patients: No dose adjustment required based on age alone, but consider taking with food to reduce exposure-related risks 1

Efficacy

Mirabegron demonstrates significant efficacy in treating OAB symptoms:

• Reduces incontinence episodes per 24 hours (mean difference -0.41 compared to placebo) 2, 3
• Decreases micturition frequency per 24 hours 2
• Increases mean volume voided per micturition 2
• Reduces urgency episodes 2, 3
• Efficacy is observed as early as 4 weeks for the 50 mg dose 4

Contraindications

• Severe uncontrolled hypertension 1
• Severe hepatic impairment 1
• End-stage renal disease 1

Adverse Events

• Common adverse events: hypertension, nasopharyngitis, urinary tract infection 1, 5
• Notably, the incidence of dry mouth (0.5-2.1%) is similar to placebo and significantly lower than with antimuscarinic agents like tolterodine (8.6%) 1, 4, 6

Monitoring Recommendations

• Assess treatment response after 4-8 weeks to determine efficacy 1
• Regular blood pressure monitoring, especially in patients with pre-existing hypertension 1
• Monitor for urinary retention and constipation 1
• Assess post-void residual if symptoms worsen 1
• Annual follow-up to reassess symptoms and treatment efficacy 1

Special Considerations

• Mirabegron is the preferred pharmacological option for elderly patients with OAB due to its better side effect profile, particularly regarding cognitive effects 1
• For patients with inadequate response to monotherapy, combination therapy with mirabegron plus solifenacin 5mg may provide improved efficacy with a side effect profile similar to monotherapy 1
• For males with Multiple Sclerosis experiencing both urinary urgency and retention, a combination of alpha-1 adrenoceptor antagonists plus mirabegron is recommended 1
• Measure post-void residual (PVR) volume before initiating therapy in patients with risk of urinary retention 1

Clinical Pearls

• Mirabegron has a different mechanism of action (β3-adrenergic receptor agonist) compared to antimuscarinic agents, making it a valuable alternative for patients who cannot tolerate antimuscarinic side effects 4
• The low incidence of dry mouth with mirabegron (compared to antimuscarinics) may improve treatment adherence, as dry mouth is often a reason for discontinuation of antimuscarinic therapy 4
• Efficacy is maintained throughout the treatment period, with significant improvements observed as early as the first assessment at week 4 4