MIRABEGRON 25MG PR TABLETS 30`S (ASTELLAS)

Mirabegron is a selective beta-3 adrenergic receptor agonist. It works by activating beta-3 receptors in the detrusor muscle (the bladder wall), causing bladder muscle relaxation during the filling phase — increasing bladder capacity, reducing urgency, and decreasing the frequency of micturition and urgency incontinence episodes. Unlike antimuscarinic drugs (oxybutynin, tolterodine), mirabegron has minimal anticholinergic side effects, making it preferable in elderly patients or those at risk of cognitive impairment.

It is used to treat the symptoms of overactive bladder (OAB) in adults — urge urinary incontinence, urgency, and urinary frequency.

Take one 25 mg prolonged-release tablet once daily, with or without food. Swallow whole — do not crush, chew, or split (this would destroy the prolonged-release mechanism). If tolerated and further reduction in symptoms is needed, the dose may be increased to 50 mg once daily after 4 weeks.

Mirabegron should not be used in: uncontrolled hypertension (SBP ≥ 180 mmHg and/or DBP ≥ 110 mmHg); severe uncontrolled hypertension; and known hypersensitivity to mirabegron or any excipient.

Use with caution in: controlled hypertension; patients with QT prolongation or on other QT-prolonging medicines (mirabegron modestly prolongs QT); severe renal impairment (eGFR < 15 — avoid; eGFR 15–29 — max 25 mg); severe hepatic impairment (Child-Pugh C — avoid); bladder outflow obstruction.

•       CYP2D6 substrates (metoprolol, flecainide, tricyclics, antipsychotics): mirabegron inhibits CYP2D6 — increases levels of these drugs; monitor for toxicity.

•       CYP3A inhibitors (ketoconazole, itraconazole): increase mirabegron exposure — max dose 25 mg in these patients.

•       Digoxin: mirabegron inhibits P-gp and increases digoxin levels — monitor digoxin levels.

•       QT-prolonging agents: additive QT prolongation — monitor ECG.

Store below 25°C. Keep in original blister packaging. Keep out of reach of children. Do not use after expiry date.

Mirabegron offers an alternative to antimuscarinic medicines (oxybutynin, solifenacin, tolterodine) for overactive bladder, particularly for patients who experience dry mouth, constipation, blurred vision, or cognitive side effects on those medicines. In elderly patients, avoiding anticholinergic drugs is especially important as they can cause confusion and increase dementia risk.

Lifestyle measures alongside mirabegron improve outcomes: timed voiding (bladder training); reducing caffeine and alcohol; limiting fluid intake in the evening; and pelvic floor exercises.

Blood pressure monitoring is important — mirabegron can raise blood pressure, particularly in patients who already have hypertension. Monitor and inform your doctor if your readings increase.

The 25 mg dose is appropriate for: patients with moderate to severe renal impairment (eGFR 30–59); patients on strong CYP3A inhibitors; and as the starting dose for all patients (can increase to 50 mg after 4 weeks).

Mirabegron modestly inhibits CYP2D6 — the most clinically relevant interaction is with metoprolol (significantly increased exposure) and flecainide (arrhythmia risk).

Check for CYP2D6 substrates with narrow therapeutic indices. Digoxin interaction via P-gp: if digoxin is co-prescribed, check baseline digoxin level before starting mirabegron and recheck after 1 week.

QTc monitoring recommended in patients on multiple QT-prolonging drugs. Mirabegron is recommended in NICE guidance (TA290) as an option when antimuscarinic drugs are not tolerated or are contraindicated.

Why does it affect my blood pressure?

Beta-3 receptors are present not just in the bladder but also in blood vessels. Activating them can cause mild arteriolar dilation but also increases cardiac output slightly, resulting in a small rise in blood pressure in some patients. This is why BP monitoring is important.

Can I take this medicine if I have a prostate problem?

Use with caution if you have benign prostatic hyperplasia (BPH) with bladder outflow obstruction — mirabegron can increase the risk of urinary retention. Discuss with your urologist.

Do I need to keep taking it long-term?

An overactive bladder is often a long-term condition. Mirabegron can be taken indefinitely if it is effective and well-tolerated. Regular reviews with your GP will assess ongoing need.

What if I miss a dose?

Take the missed dose as soon as you remember, unless it is almost time for your next dose — in that case, skip it. Do not take two doses together.

Can I take the 50 mg tablet if the 25 mg isn't working?

After 4 weeks at 25 mg, your doctor may increase to 50 mg if further symptom improvement is needed and the medicine is well tolerated. Do not increase the dose without medical advice.