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

Side Effects of Mirabegron (Beta-3 Adrenergic Agonist)

The most common side effects of mirabegron include hypertension, nasopharyngitis, urinary tract infection, and headache, with significantly fewer anticholinergic side effects compared to antimuscarinic medications. 1

Common Side Effects

• Hypertension (7.5-11.3% with 25-50mg doses) is one of the most frequently reported adverse reactions 1
• Nasopharyngitis (3.5-3.9%) and upper respiratory tract infections (1.5-2.1%) are common 1
• Urinary tract infection (2.9-4.2%) is reported more frequently than with placebo 1
• Headache (2.1-3.2%) is another common side effect 1
• Constipation (1.6%) occurs but at a lower rate than with antimuscarinic agents 1
• Diarrhea (1.2-1.5%) may occur in some patients 1
• Tachycardia (1.2-1.6%) has been reported 1
• Arthralgia (1.3-1.6%) and fatigue (1.2-1.4%) may also occur 1

Cardiovascular Effects

• Mirabegron can cause a dose-dependent increase in blood pressure (approximately 0.4-0.6 mmHg above placebo) 2
• Pulse rate increases of approximately one beat per minute have been observed 2
• The medication is contraindicated in patients with severe uncontrolled hypertension 3
• Regular blood pressure monitoring is recommended, especially during the initial treatment period 3
• Cerebrovascular accidents (0.4%) have been reported as serious adverse events 1

Serious Side Effects

• Angioedema may occur and requires immediate discontinuation if swelling of the lips, face, tongue, or throat develops 1
• Urinary retention is a potential risk, particularly in patients with bladder outlet obstruction 1
• Serious skin reactions, including urticaria, leukocytoclastic vasculitis, rash, pruritus, and lip edema have been reported, though rarely 1

Laboratory Abnormalities

• Liver enzyme elevations (GGT, AST, ALT, LDH) have been reported in less than 1% of patients 1
• Serum ALT/AST increased from baseline by greater than 10-fold has been observed in rare cases (0.3%) 1

Special Population Considerations

• Mirabegron is generally well-tolerated in elderly patients but requires careful monitoring 3
• The medication is contraindicated during pregnancy as safety has not been established 1
• Dose reduction is necessary in patients with severe renal failure or moderate hepatic failure 3
• In men with lower urinary tract symptoms, regular re-evaluation of symptoms and post-void residual volume is advised 4, 3

Drug Interactions

• Mirabegron is a moderate CYP2D6 inhibitor and may increase systemic exposure to medications metabolized by this pathway 1
• Careful monitoring is needed when co-administered with drugs having narrow therapeutic indices that are metabolized by CYP2D6 1
• Medications that may interact include thioridazine, flecainide, propafenone, and digoxin 1

Comparison with Antimuscarinic Agents

• Mirabegron has a significantly lower incidence of dry mouth (2.8%) compared to antimuscarinic medications (8.6% with tolterodine) 1, 5
• Unlike antimuscarinic agents, mirabegron does not significantly affect voiding urodynamic parameters 4
• The overall change in post-void residual volume is small with mirabegron 3
• Mirabegron may be a valuable alternative for patients who cannot tolerate antimuscarinic side effects 5

Monitoring Recommendations

• Regular blood pressure monitoring is essential, particularly in patients with pre-existing hypertension 3
• Men with lower urinary tract symptoms should be monitored for changes in voiding patterns 4
• Patients should be advised to discontinue medication if worsening voiding symptoms or urinary stream occurs 4
• Monitor for signs of angioedema, especially during initial treatment 1