Comparison of Myrbetriq (Mirabegron) vs Solifenacin for Overactive Bladder
For most patients with overactive bladder, mirabegron (Myrbetriq) is preferable to solifenacin due to its more favorable side effect profile, particularly regarding anticholinergic effects, while maintaining similar efficacy for symptom control. 1
Mechanism of Action and Indications
Mirabegron: A β3-adrenoceptor agonist that relaxes the detrusor muscle 2
- FDA-approved for overactive bladder with symptoms of urge urinary incontinence, urgency, and urinary frequency 2
Solifenacin: A muscarinic antagonist (antimuscarinic) 3
- FDA-approved for overactive bladder with symptoms of urge urinary incontinence, urgency, and urinary frequency 3
Efficacy Comparison
Both medications demonstrate similar efficacy in treating OAB symptoms:
Both medications show improvements in:
Recent evidence from a 2023 study suggests that while both medications improve OAB symptom scores, mirabegron may provide slightly better symptom improvement (OABSS score after therapy: 3.43±1.13 for mirabegron vs 4.20±1.32 for solifenacin) 4
Side Effect Profile Comparison
Mirabegron
- Most common adverse effects:
Solifenacin
- Most common adverse effects:
Patient Selection Algorithm
First-line approach: Begin with behavioral therapies for all patients (bladder training, pelvic floor muscle training, fluid management) 5
If behavioral therapy is insufficient, select medication based on:
- For patients with cognitive concerns or elderly patients: Choose mirabegron (fewer cognitive side effects)
- For patients with hypertension concerns: Choose solifenacin (with blood pressure monitoring)
- For patients with constipation history: Choose mirabegron
- For patients with urinary retention risk: Choose mirabegron (less risk of retention)
Dosing considerations:
- Mirabegron: Start at 25 mg once daily, may increase to 50 mg after 4-8 weeks if needed 2
- Solifenacin: Typically 5 mg once daily, may increase to 10 mg if needed
Combination Therapy
For patients with inadequate response to monotherapy, combination therapy may be considered:
- The 2019 AUA/SUFU guideline supports combination therapy with an antimuscarinic and β3-adrenoceptor agonist for patients refractory to monotherapy 5
- Combination of solifenacin 5 mg and mirabegron 50 mg has shown superior efficacy compared to either medication alone 5, 6, 7
- Combination therapy appears to have additive effects on symptom improvement 7
- However, combination therapy is associated with slightly higher rates of adverse events 5, 7
Special Populations
Elderly Patients
- Mirabegron is generally better tolerated in elderly patients due to fewer anticholinergic effects 8
- Solifenacin should be used with caution in elderly patients due to risk of cognitive impairment
Patients with Comorbidities
- Narrow-angle glaucoma: Avoid solifenacin unless approved by ophthalmologist 5
- Impaired gastric emptying/history of urinary retention: Use solifenacin with extreme caution 5
- Hypertension: Monitor blood pressure with mirabegron 2
Monitoring Recommendations
- For mirabegron: Monitor blood pressure periodically, especially in hypertensive patients 2
- For solifenacin: Monitor for urinary retention, especially in patients with bladder outlet obstruction
- For both: Assess symptom improvement and side effects after 4-8 weeks of therapy
Common Pitfalls to Avoid
- Failing to start with behavioral therapies before medication
- Not considering anticholinergic burden in elderly patients when prescribing solifenacin
- Inadequate blood pressure monitoring with mirabegron
- Not assessing post-void residual in at-risk patients before starting solifenacin
- Overlooking the potential for combination therapy in refractory cases