Iretig (Mirabegron)

Mirabegron acts on the lower urinary tract to improve storage function in patients with overactive bladder and related conditions.

• Overactive bladder: increases bladder capacity and reduces urgency episodes.
• Urinary urgency: lessens the intensity and frequency of sudden urges to void.
• Urge urinary incontinence: decreases the number of incontinence episodes.
• Nocturia: reduces nighttime urinary frequency.

• Mirabegron selectively stimulates β3‑adrenergic receptors in the detrusor smooth muscle of the bladder. Activation of these receptors leads to relaxation of the detrusor during the storage phase, thereby increasing functional bladder capacity and reducing involuntary contractions that cause urgency and frequency.

Adverse reactions may occur with mirabegron therapy. Most are mild and reversible, but serious events are reported in a minority of patients.

Common Side Effects

• Hypertension: elevated blood pressure observed in some patients.
• Nasopharyngitis: mild upper respiratory tract infection symptoms.
• Urinary tract infection: increased incidence of bacterial urinary infections.
• Headache: transient head discomfort.

Serious or Rare Side Effects

• Urinary retention: difficulty emptying the bladder.
• Tachycardia: rapid heart rate that may require monitoring.
• Angioedema: swelling of face, lips or throat, potentially life‑threatening.

Before initiating mirabegron, clinicians should consider several safety aspects.

• Blood pressure monitoring: check baseline and periodically during therapy.
• Cardiovascular assessment: evaluate for uncontrolled hypertension or arrhythmias.
• Renal function review: adjust use in patients with severe renal impairment.
• Urinary retention risk: monitor for signs of incomplete bladder emptying.
• Contraindication in uncontrolled hypertension: avoid use if systolic pressure >180 mmHg.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Mirabegron can alter the pharmacokinetics of several co‑administered medicines.

Major Interactions (Avoid)

• Strong CYP2D6 inhibitors (e.g., paroxetine, quinidine): may increase mirabegron exposure.
• Digoxin: mirabegron can raise digoxin plasma levels, risking toxicity.

Moderate Interactions (Monitor Closely)

• Moderate CYP2D6 inhibitors (e.g., fluoxetine, sertraline): may modestly increase mirabegron levels.
• Metoprolol and other β‑blockers: mirabegron may enhance their effects, requiring dose adjustment.
• Anticholinergic agents used for bladder control: combined use may increase anticholinergic burden.