Adverse Effects of Mirabegron
Mirabegron is generally well-tolerated with the most frequent adverse effects being hypertension, urinary tract infections, headache, and nasopharyngitis, and it is contraindicated in patients with severe uncontrolled hypertension. 1
Most Common Adverse Effects (>2% incidence)
Based on FDA-approved labeling from large clinical trials, the most commonly reported adverse reactions include 1:
- Hypertension (7.5-11.3% vs 7.6% placebo) - predominantly in patients with baseline hypertension
- Nasopharyngitis (3.5-3.9% vs 2.5% placebo)
- Urinary tract infection (2.9-4.2% vs 1.8% placebo)
- Headache (2.1-3.2% vs 3.0% placebo)
- Constipation (1.6% vs 1.4% placebo)
- Tachycardia (1.2-1.6% vs 0.6% placebo)
The 2023 European Association of Urology guidelines confirm these findings, noting that mirabegron is well tolerated in elderly patients and those with multiple comorbidities 2.
Cardiovascular Considerations
Blood pressure monitoring is essential, particularly during initiation. The drug causes small increases in systolic and diastolic blood pressure 1. Mirabegron is absolutely contraindicated in severe uncontrolled hypertension 2, 1. Recent evidence suggests it can be used cautiously in patients with well-controlled hypertension, though 6.5% may experience blood pressure increases requiring discontinuation 3.
Less Common but Clinically Important Adverse Effects (<1% incidence)
From FDA labeling 1:
- Cardiac: Palpitations, atrial fibrillation (0.2%)
- Gastrointestinal: Dyspepsia, gastritis, abdominal distension
- Hepatic: Elevated liver enzymes (GGT, AST, ALT, LDH)
- Ophthalmologic: Glaucoma, blurred vision
- Dermatologic: Urticaria, leukocytoclastic vasculitis, rash, pruritus
- Genitourinary: Nephrolithiasis, bladder pain
Serious Adverse Events
Angioedema can occur and requires immediate discontinuation if tongue, hypopharynx, or larynx involvement occurs 1. In long-term studies, cerebrovascular accidents (0.4%) and neoplasms (including breast, lung, and prostate cancer) were reported, though causality was not established 1.
Discontinuation Rates
Treatment discontinuation due to adverse effects occurs in approximately 1-3% of patients 1. The most frequent reasons include nausea, headache, hypertension, diarrhea, constipation, dizziness, and tachycardia (all ≥0.2%) 1.
Comparative Safety Profile
Mirabegron has distinct advantages over antimuscarinics: it does not cause dry mouth at the same frequency (2.8% vs 8.6% for active antimuscarinic control), does not significantly affect voiding parameters, and produces minimal changes in post-void residual volume 2. The 2014 American College of Physicians guidelines note that nasopharyngitis and gastrointestinal disorders are more common with mirabegron than placebo, but the drug avoids the anticholinergic burden of traditional OAB medications 4.
Special Populations
Elderly and frail patients: Mirabegron is well-tolerated with no dose adjustment needed based on age alone 1, 5. However, pediatric patients under 12 years, especially those under 8 years, show larger increases in blood pressure and should take the medication with food to reduce exposure-related risks 1.
Drug Interactions
Mirabegron is a moderate CYP2D6 inhibitor, requiring dose adjustments for narrow therapeutic index drugs metabolized by this pathway 1.
Clinical Pitfalls to Avoid
- Do not prescribe to patients with severe uncontrolled hypertension (absolute contraindication)
- Monitor blood pressure at baseline and periodically, especially in the first 3 months
- Avoid in severe renal impairment (eGFR <15 mL/min) or severe hepatic impairment (Child-Pugh C)
- Reduce dose to 25 mg in moderate hepatic impairment or severe renal impairment (eGFR 15-29 mL/min)
- Watch for angioedema symptoms and discontinue immediately if airway involvement occurs