Drug Groups

approved; investigational

Description

Oxybutynin is an anticholinergic medication used to relieve urinary and bladder difficulties, including frequent urination and inability to control urination, by decreasing muscle spasms of the bladder. It competitively antagonizes the M1, M2, and M3 subtypes of the muscarinic acetylcholine receptor.

Indication

For the treatment of overactive bladder.

Pharmacology

Oxybutynin is an antispasmodic, anticholinergic agent indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency. Oxybutynin relaxes bladder smooth muscle. Oxybutynin exhibits only one-fifth of the anticholinergic activity of atropine on the rabbit detrusor muscle, but four to ten times the antispasmodic activity. Antimuscarinic activity resides predominantly in the R-isomer.

Toxicity

LD₅₀=1220 mg/kg (Orally in rats, Goldenthal)

Affected Organisms

Biotransformation

Hepatic, primarily by CYP3A4

Absorption

Rapidly absorbed from gastrointestinal tract.

Half Life

12.4-13.2 hours

Protein Binding

91%-93%

Elimination

Oxybutynin is metabolized primarily by the cytochrome P450 enzyme systems, particularly CYP3A4, found mostly in the liver and gut wall. Oxybutynin is extensively metabolized by the liver, with less than 0.1% of the administered dose excreted unchanged in the urine.
Also, less than 0.1% of the administered dose is excreted as the metabolite N-desethyloxybutynin.

Distribution

* 193 L

References

External Links