What is the recommended dosing for Myrbetriq (mirabegron) in treating overactive bladder?

Recommended Dosing for Myrbetriq (Mirabegron) in Treating Overactive Bladder

The recommended starting dose of Myrbetriq (mirabegron) for treating overactive bladder in adults is 25 mg orally once daily, which may be increased to 50 mg once daily after 4-8 weeks if needed and tolerated. 1, 2

Standard Dosing Protocol

• Initial dose: 25 mg orally once daily 1
• Dose adjustment: May increase to 50 mg once daily after 4-8 weeks if needed for better symptom control 1, 2
• Administration: Swallow tablets whole with water; do not chew, divide, or crush 1
• Timing: Can be taken with or without food for adults 1

Dosing in Special Populations

Renal Impairment

• Moderate renal impairment (eGFR 30-89 mL/min/1.73 m²): No dose adjustment needed
• Severe renal impairment (eGFR 15-29 mL/min/1.73 m²): Maximum recommended dose is 25 mg once daily
• End-stage renal disease: Not recommended 1

Hepatic Impairment

• Mild to moderate hepatic impairment (Child-Pugh Class A or B): No dose adjustment needed
• Severe hepatic impairment (Child-Pugh Class C): Not recommended 1

Elderly Patients

• Standard dosing can be used in elderly patients
• Efficacy and safety are not substantially different in older patients 2
• Mirabegron is preferred over antimuscarinics in elderly patients due to lower risk of cognitive side effects 2

Monitoring and Safety Considerations

• Blood pressure monitoring: Regular monitoring is recommended, especially in patients with pre-existing hypertension 2
• Urinary retention: Monitor for signs of urinary retention, particularly in patients with bladder outlet obstruction or those taking muscarinic antagonist drugs 1
• Post-void residual volume: Consider checking in patients at risk for urinary retention 2
• Drug interactions:
  • Use caution with CYP2D6 substrates (especially narrow therapeutic index drugs) 1
  • When used with digoxin, start with the lowest dose of digoxin and monitor serum levels 1

Common Adverse Events

• Hypertension
• Nasopharyngitis
• Urinary tract infection
• Headache 1, 3

The incidence of dry mouth with mirabegron is similar to placebo and significantly lower than with antimuscarinic medications, making it a good option for patients who cannot tolerate the side effects of antimuscarinics 4.

Clinical Pearls

• Mirabegron works through a different mechanism of action than antimuscarinic agents (β3-adrenergic receptor agonist) 3
• Significant improvements in OAB symptoms can be seen as early as 4 weeks after initiating treatment 4
• Mirabegron carries a low risk of QT interval prolongation 3
• For patients with persistent OAB symptoms despite monotherapy, combination therapy with mirabegron plus an antimuscarinic (preferably solifenacin 5 mg) may be considered 2

Mirabegron provides a clinically meaningful benefit in treating OAB symptoms with a favorable tolerability profile compared to antimuscarinic medications, particularly regarding dry mouth and constipation 3, 4.