Mirabegron

How it works

By activating detrusor beta-3 adrenoceptors it relaxes the bladder wall during filling, improving storage symptoms without the dry mouth and constipation typical of antimuscarinics.

Prescribing in practice

• Because it can increase blood pressure, it must not be used in severe uncontrolled hypertension and blood pressure should be checked at baseline and on treatment.
• It is generally better tolerated than antimuscarinics in older people but should still be used cautiously where there is bladder outflow obstruction or concomitant antimuscarinics, given a risk of urinary retention.
• As a moderate CYP2D6 inhibitor it can raise levels of narrow-margin substrates, so screen for interactions.

Monitoring

Monitor blood pressure during therapy and reassess overactive-bladder symptoms after an adequate trial.

Counselling the patient

• Take once daily with water, with or without food.
• Report inability to pass urine or any swelling of the face, lips or throat promptly.

Evidence & guidelines

NICE supports mirabegron for overactive bladder when antimuscarinics are unsuitable, ineffective or poorly tolerated, based on trial evidence of symptom improvement.