What are the side effects of Mirabegron (beta-3 adrenergic agonist)?

Mirabegron Side Effects

Mirabegron is generally well tolerated with the most frequent adverse effects being hypertension, urinary tract infections, headache, and nasopharyngitis, while notably causing significantly less dry mouth compared to antimuscarinic medications. 1, 2

Most Common Adverse Effects (>2% incidence)

According to the 2023 European Association of Urology guidelines and FDA labeling data, the most frequently reported adverse effects include:

• Hypertension (7.5-11.3% vs 7.6% placebo): This is the most significant concern and occurs predominantly in patients with baseline hypertension 1, 2
• Nasopharyngitis (3.5-3.9% vs 2.5% placebo) 1, 2
• Urinary tract infections (2.9-4.2% vs 1.8% placebo) 1, 2
• Headache (2.1-3.2% vs 3.0% placebo) 1, 2
• Constipation (1.6% vs 1.4% placebo) 1, 2
• Tachycardia (1.2-1.6% vs 0.6% placebo) 2

Cardiovascular Effects - Critical Monitoring Required

Blood pressure monitoring is essential during mirabegron therapy, particularly during the initial treatment period. 3

• Mirabegron can cause dose-dependent increases in blood pressure 4
• The drug is contraindicated in patients with severe uncontrolled hypertension 1, 3
• Cardiac arrhythmias, especially tachycardia, can occur 4
• Palpitations and blood pressure increases have been reported in <1% of patients 2

Advantages Over Antimuscarinic Medications

Dry mouth occurs in only 0.5-2.1% of mirabegron patients compared to 8.6% with antimuscarinic drugs, representing a three to fivefold reduction. 2, 5

• This lower incidence of anticholinergic side effects is a major advantage, as dry mouth is the most bothersome adverse effect leading to antimuscarinic discontinuation 5
• Mirabegron does not significantly affect voiding urodynamic parameters, and overall change in post-void residual volume is small 1

Less Common but Important Adverse Effects (<1% incidence)

The FDA labeling and European guidelines document additional adverse effects occurring in <1% of patients:

• Gastrointestinal: Dyspepsia, gastritis, abdominal distension, diarrhea (1.2-1.5%) 2
• Renal/urinary: Nephrolithiasis (kidney stones), bladder pain 2
• Dermatologic: Urticaria, leukocytoclastic vasculitis, rash, pruritus, purpura, lip edema 2
• Ophthalmologic: Glaucoma, dry eyes, blurred vision 2
• Laboratory abnormalities: Elevated GGT, AST, ALT, and LDH 2
• Reproductive: Vulvovaginal pruritus, vaginal infection 2

Serious Adverse Events

• Angioedema: Rare but potentially life-threatening allergic reaction with swelling of lips, face, tongue, or throat with or without difficulty breathing 2
• Urinary retention: May increase risk in patients with bladder outlet obstruction or when combined with other overactive bladder medications 2
• Atrial fibrillation (0.2%) and cerebrovascular accident (0.4%) were reported in long-term studies 2
• Hepatotoxicity: Two patients (0.3%) experienced >10-fold increases in ALT/AST, which resolved while continuing treatment 2

Discontinuation Rates Due to Adverse Effects

The most frequent adverse events leading to discontinuation (≥0.2%) in clinical trials were:

• Nausea, headache, hypertension, diarrhea, constipation, dizziness, and tachycardia 2
• Overall discontinuation rates due to adverse effects were low, with solifenacin showing the lowest risk among overactive bladder medications 1

Special Population Considerations

Mirabegron is well tolerated in elderly patients (≥65 years) and those with multiple comorbidities. 1, 6, 7

• In a recent 2025 study of hypertensive women, 78.2% experienced no side effects, while only 6.5% had blood pressure increases requiring drug discontinuation 8
• Long-term safety data (up to 12 months) support continued use in appropriate patients 1, 5

Critical Contraindications and Precautions

• Absolute contraindication: Severe uncontrolled hypertension 1, 3
• Drug interactions: Mirabegron is a moderate CYP2D6 inhibitor, requiring dose adjustments for narrow therapeutic index drugs metabolized by this pathway (thioridazine, flecainide, propafenone, digoxin) 2
• Pregnancy: Insufficient data; should not be used in women who are or may be pregnant 4

Long-Term Safety Profile

Long-term data on efficacy and safety of mirabegron in men of any age with lower urinary tract symptoms are not available. 1

• Studies up to 12 months demonstrate maintained efficacy with acceptable tolerability 1, 5
• No causal relationship has been established between mirabegron and neoplasms reported in clinical trials (breast cancer, lung cancer, prostate cancer at 1.3% in the 100mg group) 2