| Indication |
For the treatment of overactive bladder. |
| Pharmacodynamics |
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. |
| Mechanism of action |
Oxybutynin exerts a direct antispasmodic effect on smooth muscle
and inhibits the muscarinic action of acetylcholine on smooth muscle. No
blocking effects occur at skeletal neuromuscular junctions or autonomic
ganglia (antinicotinic effects). By inhibiting particularily the M1 and
M2 receptors of the bladder, detrusor activity is markedly decreased. |
| Absorption |
Rapidly absorbed from gastrointestinal tract. |
| Volume of distribution |
|
| Protein binding |
91%-93% |
| Metabolism |
Hepatic, primarily by CYP3A4 |
| Route of 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. |
| Half life |
12.4-13.2 hours |
| Clearance |
Not Available |
| Toxicity |
LD50=1220 mg/kg (Orally in rats, Goldenthal) |
