Mirabegron

• Mirabegron is indicated for conditions within the overactive bladder disease spectrum, where it improves bladder function.
• Overactive bladder: reduces urgency, frequency, and urge urinary incontinence episodes.
• Urge urinary incontinence: decreases the number of incontinence events.
• Frequency of urination: lowers daytime urinary frequency.

• Mirabegron selectively stimulates β3‑adrenergic receptors located in the detrusor smooth muscle of the bladder. Activation of these receptors raises cyclic adenosine monophosphate (cAMP) levels, causing relaxation of the detrusor muscle during the storage phase. This relaxation expands bladder capacity, diminishes involuntary contractions, and consequently reduces urgency and frequency of voiding.

Mirabegron may be associated with a range of adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Hypertension: elevated blood pressure observed in some patients.
• Nasopharyngitis: mild upper respiratory tract infection.
• Urinary tract infection: increased incidence reported.
• Headache: occasional mild to moderate headache.
• Constipation: reduced bowel movements.
• Dry mouth: decreased salivation.

Serious or Rare Side Effects

• Severe hypertension: marked increase in blood pressure requiring medical attention.
• Urinary retention: difficulty emptying the bladder.
• Tachycardia: rapid heart rate episodes.
• Angioedema: swelling of face, lips, or throat.
• Myocardial infarction: rare cardiac event.
• Acute renal failure: sudden loss of kidney function.

• When prescribing Mirabegron, clinicians should consider several safety precautions to minimize risk.
• Assess blood pressure before initiating therapy: baseline measurement recommended.
• Monitor for hypertension during treatment: check blood pressure regularly.
• Evaluate renal function: adjust dose in severe impairment.
• Use caution in hepatic impairment: consider dose reduction.
• Avoid use in uncontrolled hypertension: contraindicated.
• Store at ambient temperature: keep in the original pack, protect from moisture.

Mirabegron can affect the pharmacokinetics of other medicines, requiring attention to potential drug‑drug interactions.

Major Interactions (Avoid)

• Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine): may increase Mirabegron exposure.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may raise plasma levels.
• Concomitant antihypertensive agents: may reduce their efficacy, leading to uncontrolled blood pressure.

Moderate Interactions (Monitor Closely)

• Anticholinergic agents: may increase anticholinergic burden.
• Diuretics: may enhance risk of hypertension.
• CYP2D6 substrates (e.g., metoprolol): may have altered plasma concentrations.