Mirabegron Side Effects
Mirabegron is generally well-tolerated with a favorable safety profile, but clinicians must monitor for three serious adverse effects: increased blood pressure, urinary retention, and angioedema, while common side effects include nasopharyngitis, urinary tract infections, headache, and constipation. 1
Serious Side Effects Requiring Monitoring
Increased Blood Pressure
- Mirabegron can cause blood pressure elevation or worsen pre-existing hypertension 1
- Blood pressure monitoring is mandatory during treatment 1
- Patients with very high uncontrolled blood pressure should not initiate therapy 1
- In clinical trials, hypertension was reported as a common adverse event in adults with overactive bladder 1
Urinary Retention
- Risk is significantly elevated in patients with bladder outlet obstruction or those taking concurrent antimuscarinic medications 1
- Events indicative of urinary retention were reported more frequently in combination therapy (mirabegron plus antimuscarinics) compared to monotherapy 2
- Patients unable to empty their bladder should contact their physician immediately 1
Angioedema
- Can present as swelling of lips, face, tongue, or throat with or without difficulty breathing 1
- Requires immediate discontinuation and emergency medical attention 1
- Patients should also watch for hives, skin rash, or itching 1
Common Side Effects in Adults with Overactive Bladder
The most frequently reported adverse events include:
- Nasopharyngitis (pain or swelling of nose/throat) - confirmed as the most common side effect in meta-analysis (OR 1.54,95% CI 1.05-2.25) 3, 1
- Urinary tract infection 1
- Headache 1
- High blood pressure 1
Common Side Effects in Children with Neurogenic Detrusor Overactivity
Pediatric patients experience a slightly different profile:
In pediatric studies, additional adverse reactions leading to discontinuation included dry mouth, headaches, dizziness, nausea/vomiting, increased seizures, and rash 4
Combination Therapy Considerations
When mirabegron is combined with antimuscarinics (particularly solifenacin), adverse events increase modestly but remain generally tolerable:
- Treatment-emergent adverse events occurred in 49% of combination therapy patients versus 41% with mirabegron monotherapy and 44% with solifenacin monotherapy 2
- Dry mouth was the most commonly reported adverse event in combination therapy 2
- Constipation and dyspepsia were slightly increased in combination groups 2
- Urinary retention events were more frequent with combination therapy 2
Comparative Safety Profile
Mirabegron demonstrates superior tolerability compared to antimuscarinics for anticholinergic side effects:
- Significantly better tolerated than 21/22 active comparators regarding dry mouth 5
- Better tolerated than 9/20 comparators for constipation 5
- Better tolerated than 7/10 comparators for urinary retention 5
- Overall adverse events were lower with mirabegron 50 mg versus tolterodine 4 mg (OR 0.71,95% CI 0.59-0.86) 6
Special Population Considerations
Elderly Patients (≥65 years)
- Safety and tolerability in patients aged ≥65 years were consistent with the known mirabegron safety profile 7
- In very elderly women (>80 years), no significant differences in blood pressure or heart rate were observed before and after treatment 8
Cardiovascular Effects
- Recent evidence suggests mirabegron's positive chronotropic effects are primarily mediated through β1-adrenoceptors rather than β3-adrenoceptors 9
- This mechanism may explain cardiovascular side effects and warrants ECG monitoring in at-risk patients 4
Clinical Monitoring Recommendations
Based on FDA labeling and clinical trial data:
- Regular blood pressure checks during treatment 1
- Post-void residual assessment in patients with bladder outlet obstruction 1
- ECG monitoring when clinically indicated, particularly in patients with cardiovascular risk factors 4
- Evaluation for urinary retention symptoms, especially with combination therapy 2