What is the recommended treatment and dosage for overactive bladder using Myrbetriq (mirabegron)?

Mirabegron (Myrbetriq) Treatment for Overactive Bladder

The recommended treatment for overactive bladder using Myrbetriq (mirabegron) is to start with 25 mg orally once daily, with the option to increase to 50 mg once daily after 4-8 weeks if needed for symptom control. 1

Dosing Recommendations

• The FDA-approved starting dose for mirabegron in adults with overactive bladder is 25 mg orally once daily 1
• If needed for better symptom control, the dose may be increased to a maximum of 50 mg orally once daily after 4-8 weeks of treatment 1
• Mirabegron demonstrates dose-dependent improvements in OAB symptoms, with significant reductions in micturition frequency, urgency episodes, and incontinence episodes compared to placebo 2

Dosage Adjustments for Special Populations

Renal Impairment

• For patients with eGFR 30-89 mL/min/1.73 m², use the standard dosing of 25 mg initially with maximum 50 mg 1
• For patients with eGFR 15-29 mL/min/1.73 m², limit maximum dose to 25 mg once daily 1
• Not recommended for patients with eGFR <15 mL/min/1.73 m² or requiring dialysis 1

Hepatic Impairment

• For mild hepatic impairment (Child-Pugh Class A): standard dosing of 25 mg initially with maximum 50 mg 1
• For moderate hepatic impairment (Child-Pugh Class B): limit maximum dose to 25 mg once daily 1
• Not recommended for patients with severe hepatic impairment (Child-Pugh Class C) 1

Efficacy and Clinical Benefits

• Mirabegron significantly reduces key OAB symptoms including:

  • Micturition frequency (urinary frequency) 3
  • Urgency urinary incontinence episodes 3
  • Urgency episodes 3
  • Increases volume voided per micturition 4

• Clinical improvements are typically observed as early as 4 weeks after treatment initiation and are maintained throughout treatment 5

• Mirabegron 25 mg has demonstrated safety and therapeutic efficacy in older patients with overactive bladder and multiple comorbidities 6, 7

Combination Therapy Options

• For patients with inadequate response to mirabegron monotherapy over a 6-month period, combination therapy with an antimuscarinic agent may be considered 6, 8

• Combination of mirabegron 50 mg plus solifenacin 5 mg has shown superior efficacy compared to either monotherapy for reducing:

  • Urinary incontinence episodes 3, 8
  • Micturition frequency 3, 8
  • Urgency episodes 3, 8
  • Nocturia 3

• The SYNERGY and SYNERGY II trials demonstrated that combination therapy was statistically superior to mirabegron and solifenacin monotherapy for decreasing incontinence episodes and micturitions 3, 6

Safety and Tolerability

• Mirabegron has a favorable tolerability profile compared to antimuscarinic agents, with dry mouth rates similar to placebo 4, 5

• The most common adverse events observed in clinical trials include:

  • Hypertension 9
  • Nasopharyngitis 9
  • Urinary tract infection 9

• Regular blood pressure monitoring is recommended, especially during the initial treatment period and for patients with pre-existing hypertension 6

• Treatment-emergent adverse events were reported in 49% of patients on combination therapy (mirabegron plus solifenacin), compared to 41% with mirabegron monotherapy and 44% with solifenacin monotherapy 3

Clinical Pearls and Caveats

• Mirabegron works through a different mechanism of action (β3-adrenoceptor agonist) compared to antimuscarinic agents, making it a valuable alternative for patients who cannot tolerate antimuscarinic side effects 5

• For men with lower urinary tract symptoms and overactive bladder, regular re-evaluation of symptoms and post-void residual volume is advised 6

• Patients should be instructed to discontinue medication if they experience worsening voiding symptoms or urinary stream after starting therapy 6

• Mirabegron carries a low risk of QT interval prolongation 4

• Long-term safety data from clinical trials support the use of mirabegron for extended treatment periods 6, 9