Bethanechol

Bethanechol:
• main drug in this group; ester of choline that is structurally similar to acetylcholine
• binds directly to muscarnic receptor  activation; no effect on nicotinic receptors at therapeutic doses
• effects – decrease heart rate; increased 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  relaxation  vasodilation; in eye  miosis (pupillary constriction) and contraction of ciliary muscle (for near vision)
• used for urinary retention (especially postoperatively)  muscarnic activation relaxes urinary sphincter
• side effects – due to full range of muscarinic effects – eg hypotension, bradycardia, GI distress
• poorly absorbed from GI tract

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