oxybutynine

Oxybutynin is an antimuscarinic medication used to treat symptoms of overactive bladder, including urgency, frequency, and urge incontinence. It works by blocking muscarinic acetylcholine receptors in the detrusor smooth muscle of the bladder, which reduces involuntary contractions and increases bladder capacity. The drug acts on several muscarinic receptor subtypes, with the M3 receptor primarily mediating bladder contractions, but its metabolites can contribute to broader anticholinergic effects.

Common indications include overactive bladder in adults and neurogenic detrusor overactivity in conditions such as spinal cord injury or multiple sclerosis. Oxybutynin is available in oral forms—immediate-release and extended-release tablets—as well as a transdermal patch (Oxytrol) that provides a continuous, lower-dose exposure.

Adverse effects are typical of anticholinergic agents and include dry mouth, constipation, blurred vision, dizziness, and cognitive effects, especially in older adults. Urinary retention, reduced sweating, and heat intolerance can also occur. Anticholinergic burden may worsen cognitive function in susceptible individuals.

Contraindications and precautions include urinary retention, uncontrolled narrow-angle glaucoma, gastric outlet or severe gastroparesis, and myasthenia gravis. Caution is advised in the elderly and in patients with hepatic impairment; use during pregnancy and lactation should be guided by risk and benefit. Coadministration with other antimuscarinic drugs or CNS depressants can increase anticholinergic side effects.

Pharmacokinetics involve oral absorption with metabolism in the liver to active and inactive metabolites; the transdermal patch bypasses first-pass metabolism and provides steady systemic exposure.