Synthetic Cholinergic Blocking Agents

The aminoalcohol portion of cucatropine may be eonsid-ered a simplification of the atropine molecule. In eucalrop-ine, the bicyclic tropine has been replaced by a monocyclic aminoalcohol and mandelic acid replaces tropic acid (see under Products ). 

Another important feature in many of the synthetic anli-chulincrgics used as antispasmodics is that they contain a quaternary nitrogen, presumably to enhance activity. The initial. synthetic quaternary compound mcthantheline bromide has served as a forerunner for many others. Thc.se compounds combine anticholinergic activity of the antimuscar-inic type with some ganglionic blockade to reinfoax the parasympathetic blockade. Formation of a quaternary ammonium moiety, however, introduces the pu.ssibility of blockade of voluntary synapses (curariform activity) this can become evident with sufficiently high doses. 

The antimu.scarinic compounds now in u.se arc described in the following monographs. 

Clidinium Bromide, U5P. Clidinium bromide. 3-hy-droxy-l-methylquinuclidinium bromide ben/ilatc (Quar- 

DIcydomine Hydrochloride, USP. Dicyclomine hy. drochloride, 2-(diethylamino)ethyl bicyclohcxyl-l-carbox-ylate hydrochloride (Bentyl). has. some muscarinic receptor subtype. selectivity. It binds more firmly to Mi and Mttlian to M and Mj receptors.  

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The cholinergic blocking agents which mainly include atropine and related alkaloid are obtained from the plant Atropa belladonna (deadly nightshade), Atropa acuminata, Hyoscyamus niger (black henbane) and Datura stramonium (datura) and semisynthetic atropine/hyoscine analogues and synthetic compounds. 

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