Bethanechol is an ester of choline that is structurally similar to acetylcholine and is mainly used to treat urinary retention following a general anesthetic via muscarnic activation relaxing the urinary sphincter and causing contraction of the bladder leading to an expulsion of urine. In addition to postoperative use, it is also used for urinary retention postpartum and for neurogenic atony of the bladder.
Bethanechol binds directly to muscarnic receptors to activate them and stimulates the parasympathetic nervous system. It has no effect on the nicotinic receptors at therapeutic doses. The effects of this are to decrease heart rate; increase secretion from exocrine glands (sweating, salivation, bronchial, gastric juices); contraction of bronchi and bladder; increased tone and motility of gastrointestinal smooth muscle; in vascular smooth muscle there is a relaxation leading to vasodilation; in the eye there is a miosis (pupillary constriction) and contraction of ciliary muscle (for near vision). In contrast to acetylcholine, bethanechol is not hydrolyzed by cholinesterase and will have a longer duration of action.
The side effects are due to the range of muscarinic effects – eg hypotension, bradycardia, GI distress. The parasympathomimetic action of this drug will exacerbate the symptoms of asthma, coronary insufficiency, peptic ulcers, intestinal obstruction and hyperthyroidism, so is contraindicated in these conditions.
Trade names: Urecholine (Merck Frosst), Duvoid (Roberts), Uro-Carb (Hamilton)
Chemical Formula: C7H17N2O2
Other Cholinergic agonists:
| Choline Esters: | Alkaloids: |
| Acetylcholine | Muscarine |
| Methacholine | Pilocarpine |
| Carbachol | |
| Bethanechol |
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