Direct Measurement of the Anticholinergic Activity of a Series of Pharmacological Compounds on the Canine and Rabbit Urinary Bladder

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Abstract
Antimuscarinic therapy is used widely in the treatment of urine storage failure. Examples of antimuscarinic agents used clinically include atropine, propantheline bromide and glycopyrrolate. Other agents used in clinical urology that are believed to act at least in part by antimuscarinic activity include oxybutynin, imipramine and dicyclomine. These studies were designed to determine the relative potency of a variety of agents to compete directly for muscarinic cholinergic receptors isolated from the canine and rabbit urinary bladder. Radio-ligand binding assays for muscarinic receptors were performed with 10 nM 3H-QNB and various concentrations of the drugs under study. Of the agents tested, propantheline bromide, atropine, and glycopyrrolate were the potent muscarinic antagonists/unit of concentration. Oxybutynin and dicyclomine hydrochloride were 30 to 50 times less potent than atropine. Chlorpromazine and desmethylimipramine were approximately 500 times less potent than atropine. As expected, agents such as guanethidine, tranylcypramine and hexamethonium possessed little antimuscarinic activity.