Bethanechol structure

Molecular structures of four choline esters. Acetylcholine and methacholine are acetic acid esters of choline and -methylcholine, respectively. Carbachol and bethanechol are carbamic acid esters of the same alcohols. 

Bethanechol [be THAN e kole] is structurally related to acetylcholine the acetate is replaced by carbamate and the choline is methylated (see Figure 4.5). Hence, it is not hydrolyzed by acetylcholinesterase, although it is inactivated through hydrolysis by other esterases. It has little or no nicotinic actions but does have strong muscarinic activity. Its major actions are on the smooth musculature of the bladder and gastrointestinal tract. It has a duration of action of about 1 hour. 

Bethanechol incorporates the stabilizing structural features of both methacholine and carbachol. Thus it is like carbachol in that no appreciable cholinesterase hydrolysis takes place, and like methacholine it does not stimulate ganglia or skeletal muscle. This dmg appears to show some specificity of action in the gastrointestinal and urinary tracts. Thus, it has clinical applications in postoperative distention of the abdomen and bladder in the latter case it relieves the urinary retention that results following surgery. The drug is even orally effective. 

Bethanechol has a chemical structure that is intermediate between those of methacholine and carbachol. It is thus both long acting and selective for muscarinic receptors. 

Bethanechol (see structure above), the carbamate analogue of methacholine, is selective tor muscarinic receptors and exhibits almost no activity at nicotinic receptors, it is used to treat postsurgical and postpartum urinary retention and abdominal distention. Bethanechol is administered orally, because there is danger of a cholinergic crisis if it is given by intravenous or intramuscular injection. 

Reversible AChEls are those compounds that are substrates for and react with AChE to form an acylated enzyme, which is more stable than the acetylated enzyme but still capable of undergoing hydrolytic regeneration, or that bind to AChE with greater affinity than acetylcholine but do not react with the enzyme as a substrate. Inhibitors of both types have found clinical application. Those that acylate AChE include the aryl carbamates, such as esters of carbamic acid and phenols (e.g., physostigmine). Alkyl carbamates (esters of carbamic acid and alcohols), such as carbachol and bethanechol, both of which are structurally related to acetylcholine, also are substrates for and competitively inhibit AChE, because they are hydrolyzed very slowly by AChE. For reasons previously discussed, carbachol and ... 

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