Beta-3 agonists are a class of medications that selectively bind to and stimulate beta-3 adrenergic receptors, primarily located in the smooth muscle of the bladder.
A class of drugs that selectively stimulate β3 receptors, which are found primarily in adipose tissue, the bladder, and the heart.
By relaxing the bladder muscle (detrusor), these drugs increase bladder capacity, effectively treating overactive bladder (OAB) symptoms like sudden urges, leakage, and frequent urination.
When activated, beta-3 receptors cause the detrusor muscle to relax while the bladder fills with urine.
This allows the bladder to hold more urine without triggering the sudden, involuntary contractions that characterize OAB.
β3 receptors mediate lipolysis and thermogenesis (via brown adipose tissue).
Two primary beta-3 agonists are approved for OAB treatment:Mirabegron (Brand name: Myrbetriq)Vibegron (Brand name: Gemtesa)
Beta-3 agonists provide a major breakthrough in urology because they do not carry the troublesome side effects associated with older OAB drugs (antimuscarinics/anticholinergics).
They generally do not cause dry mouth, blurry vision, or constipation, making them much easier for patients to tolerate long-term.
Common Side The most common include:
Elevated blood pressure Urinary tract infections (UTIs, Nasopharyngitis (common cold symptoms) or sinus infections.
Headache, dizziness, or diarrhea.
β3 receptors have a minor role in cardiac relaxation (lusitropy) and are being studied in heart failure.
Advantages Over Anticholinergics (for OAB)
No dry mouth, constipation, or cognitive impairment Safer in elderly patients No risk of urinary retention as they relax, not contract
Mirabegron raises blood pressure slightly — caution in hypertension
CYP2D6 inhibition by mirabegron can increase levels of metoprolol, digoxin
Vibegron has fewer drug interactions and is preferred when polypharmacy is a concern
Investigational Areas
Heart failure (β3 cardiac effects) Metabolic syndrome / obesity Irritable bowel syndrome (smooth muscle relaxation)