beta3agonisten

Beta3-agonisten are a class of drugs that selectively activate beta-3 adrenergic receptors. In humans these receptors are found in adipose tissue and in the detrusor smooth muscle of the bladder. Activation of beta-3 receptors in the detrusor promotes relaxation of the bladder wall during the storage phase, increasing bladder capacity and reducing symptoms such as urgency, frequency, and urge incontinence.

Mechanism of action: Beta-3 receptors are Gs-protein-coupled; stimulation raises cyclic AMP levels, leading to relaxation of detrusor smooth muscle. This effect complements or replaces the antimuscarinic mechanism used by older therapies and tends to have a different side effect profile.

Clinical use: The primary indication is overactive bladder in adults, including symptoms of urgency with frequency and urge incontinence. They are used as an alternative to, or in combination with, antimuscarinics, particularly when antimuscarinics are poorly tolerated or contraindicated.

Examples: Mirabegron is the first-in-class beta-3 agonist marketed for overactive bladder (brands include Myrbetriq in the US and Betmiga in the EU). Vibegron is a newer selective beta-3 agonist approved for overactive bladder in adults (brand Gemtesa). Several other beta-3 agonists have been investigated in development.

Safety and pharmacology: Common adverse effects include hypertension, tachycardia, headache, and urinary tract infections. They may interact with antihypertensive drugs and with substrates of cytochrome P450 2D6. Caution is advised in patients with uncontrolled hypertension, significant renal impairment, or urinary retention. Beta-3 agonists are generally viewed as alternatives that avoid some anticholinergic side effects such as dry mouth or cognitive effects.