Characterization of the oxybutynin antagonism of drug-induced spasms in detrusor.
Oxybutynin chloride exerts a moderate anticholinergic effect on rabbit detrusor in vitro, which is reversible and competitive in nature (KB = 4.7 x 10(-9), and midway in potency between atropine and papaverine. In addition, oxybutynin strongly antagonizes BaCl2-induced spasms of detrusor with a potency equivalent to that of papaverine and 10 times that of atropine. This musculotropic spasmolytic effect is slightly greater in rabbit than human or monkey tissue, and noncompetitive (pD2 = 5.5). This direct relaxant effect, unlike that of papaverine, is not mediated by the inhibition of tissue phosphodiesterase, but probably reflects oxybutynin's local anesthetic properties and associated effects on Ca++ fluxes and binding.
D000818:Animals; D001464:Barium / Q000037:antagonists & inhibitors; D002217:Carbachol / Q000037:antagonists & inhibitors; D003510:Cyclohexanes / Q000494:pharmacology*; D004048:Diethylamines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D008333:Mandelic Acids / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects; D010276:Parasympatholytics; D010726:Phosphodiesterase Inhibitors; D011817:Rabbits; D001743:Urinary Bladder / Q000187:drug effects*
D003510:Cyclohexanes; D004048:Diethylamines; D008333:Mandelic Acids; D010276:Parasympatholytics; D010726:Phosphodiesterase Inhibitors; D001464:Barium; D002217:Carbachol