darifenacin

Darifenacin is a selective antimuscarinic medication used to treat symptoms of overactive bladder, such as urinary urgency, frequency, and urge incontinence. It works by blocking muscarinic receptors on the detrusor smooth muscle, with relative selectivity for the M3 receptor subtype, thereby reducing involuntary bladder contractions and increasing bladder capacity.

The drug is taken by mouth, typically as an extended-release tablet once daily. The usual starting dose is 7.5 mg once daily, with the possibility of increasing to 15 mg daily if the response is insufficient and the drug is tolerated. Brand names include Enablex in the United States and Emselex in parts of Europe.

Pharmacokinetics: Darifenacin is well absorbed after oral administration and is extensively metabolized in the liver, primarily by CYP3A4, with metabolites excreted in urine and feces. The elimination profile varies with formulation and individual factors.

Contraindications and precautions: It is contraindicated in urinary retention, gastric retention, uncontrolled narrow-angle glaucoma, severe hepatic impairment, and known hypersensitivity. Caution is advised in elderly patients and those with cognitive impairment due to the anticholinergic effects. Use during pregnancy should be considered only if clearly needed and potential benefits outweigh risks.

Interactions: Strong inhibitors of CYP3A4 (for example, certain antifungals and protease inhibitors) can raise darifenacin exposure and may necessitate dose adjustment. Concurrent use of other anticholinergic drugs can have additive effects and increase adverse outcomes.

Adverse effects: Common adverse effects include dry mouth, constipation, blurred vision, and abdominal discomfort. Less frequent but more serious reactions include urinary retention, dizziness, and tachycardia.