Mirabegron is a potent and selective beta-3 adrenergic receptor agonist used 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: Recommended starting dose is 50 mg once daily. Dose may be increased to 100 mg once daily based on individual efficacy and tolerability 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 selective agonist for beta-3 adrenergic receptors (β3-ARs). These receptors are predominantly expressed on the detrusor smooth muscle of the urinary bladder. Activation of β3-ARs stimulates adenylate cyclase, increasing intracellular cyclic AMP (cAMP). Elevated cAMP activates protein kinase A (PKA), which leads to relaxation of the detrusor muscle. This relaxation increases the bladder's storage capacity and reduces involuntary contractions (detrusor overactivity) during the filling phase, thereby alleviating the symptoms of urgency, frequency, and urge incontinence.
Pregnancy: Category C (US FDA). Animal studies have shown adverse effects (increased fetal loss, structural abnormalities). No adequate and well-controlled studies in pregnant women. Use 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 them.
| Digoxin | Mirabegron increases digoxin plasma concentration (AUC) by ~29% by inhibiting P-glycoprotein (P-gp) transport. Risk of digoxin toxicity. | Major |
| Metoprolol, Desipramine, Thioridazine | Mirabegron may increase plasma concentrations of drugs metabolized by CYP2D6 (a weak inhibitor). Monitor for increased beta-blockade or side effects. | Moderate |
| Warfarin | Potential for increased INR and bleeding risk due to increased S-warfarin levels via CYP2C9 inhibition. Monitor INR closely when starting or stopping mirabegron. | Moderate |
| Ketoconazole, Itraconazole, Clarithromycin | Strong CYP3A4 inhibitors may increase mirabegron plasma levels. Maximum dose should be limited to 50 mg once daily when co-administered. | Moderate |
| Rifampicin, Carbamazepine, Phenytoin | Strong CYP3A4 inducers may decrease mirabegron plasma levels, reducing efficacy. Consider dose adjustment (increase) based on response. | Moderate |
| Other antihypertensives | Mirabegron may attenuate the blood pressure-lowering effect. Monitor blood pressure. | Moderate |