Mirabegron is a selective beta-3 adrenergic receptor agonist used primarily for the treatment of overactive bladder (OAB) syndrome. It works by relaxing the detrusor smooth muscle of the urinary bladder during the storage phase, increasing bladder capacity and reducing the frequency of involuntary detrusor contractions. It represents a significant advancement over antimuscarinic agents due to a different mechanism of action and a potentially more favorable side effect profile, particularly regarding dry mouth and constipation.
Adult: The recommended starting dose is 25 mg once daily. Based on individual efficacy and tolerability, the dose may be increased to 50 mg once daily after 4-8 weeks.
Note: Swallow the tablet whole with a glass of water, with or without food. Do not crush, split, or chew. Should be taken at approximately the same time each day.
Mirabegron is a potent and selective agonist for the human beta-3 adrenergic receptor (β3-AR). In the urinary bladder, stimulation of β3-ARs on the detrusor smooth muscle activates Gs proteins, leading to increased intracellular cyclic adenosine monophosphate (cAMP). Elevated cAMP activates protein kinase A (PKA), which results in relaxation of the detrusor muscle. This relaxation increases bladder storage capacity and reduces the frequency and intensity of involuntary bladder contractions (detrusor overactivity) that characterize OAB.
Pregnancy: Category C (US FDA). Animal studies have shown adverse effects (increased fetal loss, delayed development). There are no adequate and well-controlled studies in pregnant women. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Driving: Dizziness, blurred vision, and fatigue have been reported. Patients should be cautioned about operating machinery or driving until they are reasonably certain that mirabegron does not adversely affect their abilities.
| Digoxin | Mirabegron increases digoxin plasma concentration (AUC) by approximately 27%. Risk of digoxin toxicity. | Major |
| Metoprolol, Propranolol (CYP2D6 substrates) | Mirabegron may increase plasma concentrations of these drugs. Monitor for increased beta-blockade effects (bradycardia, hypotension). | Moderate |
| Ketoconazole, Itraconazole, Clarithromycin (Strong CYP3A4 inhibitors) | Increase mirabegron exposure. In patients with normal renal/hepatic function, monitor for increased side effects. In patients with renal/hepatic impairment, co-administration is contraindicated. | Major |
| Rifampicin (Strong CYP3A4 inducer) | Decreases mirabegron exposure, potentially reducing efficacy. | Moderate |
| Warfarin | No significant pharmacokinetic interaction. However, monitor INR as a precaution due to potential pharmacodynamic effects on BP/HR. | Minor |
| Other antihypertensives | Mirabegron may attenuate the blood pressure-lowering effect. Monitor blood pressure regularly. | Moderate |