About Oxybutynin Antimuscarinic agent, Urinary Antispasmodic Agent. Mechanism of Action of Oxybutynin This drug decreases muscle spasms of the bladder by competitively antagonizes the M1, M2, and M3 subtypes of the muscarinic acetylcholine receptor. It also has direct spasmolytic effects on bladder smooth muscle as a calcium antagonist and local anesthetic action at high concentrations. Indications for Oxybutynin 1. Urinary incontinence 2. Urgency and frequency in the unstable bladder 3. Nocturnal enuresis