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Characterization of the Oxybutynin Antagonism of Drug-Induced Spasms in Detrusor
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1977
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Bacl2-induced SpasmsNeurophysiologyMedicinePhysiologyAnesthetic MechanismNeuropharmacologyOxybutynin AntagonismOxybutynin ChloridePharmacotherapyExperimental PharmacologyLocal Anesthetic PharmacologyNervous SystemAnesthesiaPharmacologyAnesthetic PharmacologyModerate Anticholinergic EffectNeuromuscular BlockadeAnesthesiology
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.