Bethanechol

[be-THAN-e-kole] is structurally related to acetylcholine, in which the acetate is replaced by carbamate and the choline is methylated (see Figure above). 

Hence, it is not hydrolyzed by acetylcholinesterase (due to the addition of carbonic acid), although it is inactivated through hydrolysis by other esterases. It lacks nicotinic actions (due to the addition of the methyl group) 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. 

1. Actions: Bethanechol directly stimulates muscarinic receptors, causing increased intestinal motility and tone. It also stimulates the detrusor muscles of the bladder whereas the trigone and sphincter are relaxed, causing expulsion of urine.

 2. Therapeutic applications: In urologic treatment, bethanechol is used to stimulate the atonic bladder, particularly in postpartum or postoperative, nonobstructive urinary retention. Bethanechol may also be used to treat neurogenic atony as well as megacolon.

 3. Adverse effects: Bethanechol causes the effects of generalized cholinergic stimulation (see Figure above). These include sweating, salivation, flushing, decreased blood pressure, nausea, abdominal pain, diarrhea, and bronchospasm.


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