Bethanechol

Bethanechol is a muscarinic agonist used to treat postoperative and postpartum non-obstructive functional urinary retention and neurogenic bladder atony with retention. As a cholinergic agent, bethanechol resembles the naturally occurring neurotransmitter acetylcholine in structure and pharmacological function. One advantage of bethanechol is that, unlike acetylcholine, it is not degraded by cholinesterase, which prolongs its duration of action.

Bethanechol was first synthesized in 1935.

Pharmacodynamics

Bethanechol is a direct muscarinic agonist and stimulates the parasympathetic nervous system by binding to postganglionic muscarinic receptors. This is related to its structural similarity to the natural neurotransmitter acetylcholine. Bethanechol is highly selective for muscarinic receptors and has little to no affinity for nicotinic receptors. Binding of bethanechol to M3 is most clinically significant because these receptors are present in intestinal smooth muscle and the bladder. The cholinergic effects of bethanechol result in increased detrusor muscle tone, which promotes bladder emptying, and increased smooth muscle tone, which restores gastrointestinal peristalsis and motility.

The charged quaternary amine in the structure of bethanechol prevents the compound from crossing the blood-brain barrier, minimizing associated adverse CNS effects. Due to its selectivity for muscarinic receptors, bethanechol has minimal to no nicotinic effects.

Side effects

• Hypotension
• Cardiac arrhythmias
• Dizziness
• Nausea
• Bronchial spasms

Contraindications

• Asthma
• Coronary insufficiency
• Gastric ulcers
• Intestinal obstruction
• Hyperthyroidism
• Epilepsy
• Bradycardia
• Parkinsonism
• Gastric or duodenal ulcers
• Pregnancy and lactation