Clinical Pharmacology
Oxybutynin hydrochloride exerts direct antispasmodic effect on smooth muscle and inhibits the muscarinic action of acetylcholine on smooth muscle. It exhibits one-fifth of the anticholinergic activity of atropine on the rabbit detrusor muscle, but four to ten times the antispasmodic activity. No blocking effects occur at skeletal neuromuscular junctions or autonomic ganglia (antinicotinic effects).
Sources say the drug is absorbed within one hour and has an elimination half-life of 2 to 5 hours. There is a wide variation among individuals in the drug's concentration in blood. This, and its low concentration in urine, suggest that it is eliminated through the liver.
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