Pharmacology · Muscarinic (cholinergic) agonists
Bethanechol !
A choline ester that contracts the bladder to treat urinary retention when nothing is blocking the outflow.
Updated 2026-11-01
No structure of bethanechol bound to its receptor exists. The figure shows iperoxo, a potent research agonist, in the acetylcholine (orthosteric) pocket of the active human M3 muscarinic receptor, the subtype on glands, the eye and the bladder that bethanechol stimulates.
Mechanism of action
Bethanechol is a synthetic choline ester that cholinesterase does not destroy, so it lasts longer than acetylcholine. It stimulates muscarinic receptors with little nicotinic effect: it raises the tone of the detrusor muscle enough to start urination and empty the bladder, and it increases gut tone and peristalsis. Its charged quaternary group keeps it out of the brain.
- Resists breakdown by cholinesterase
- Activates muscarinic receptors of the detrusor
- Bladder contracts and empties
- Also increases gut tone and peristalsis
Pharmacokinetics
- Absorption
- Taken by mouth, on an empty stomach to reduce nausea
- Distribution
- Does not cross the blood-brain barrier
- Metabolism
- Not destroyed by cholinesterase
Indications
- Acute postoperative and postpartum urinary retention without obstruction Acute urinary retention →
- Neurogenic atony of the bladder with retention Neurogenic bladder →
Adverse effects
Common
- Abdominal cramps, colicky pain, nausea, belching and diarrhoea
- Salivation, sweating and flushing
- Urinary urgency
- Headache
Contraindications
- Mechanical obstruction of the bladder outlet or gut, or doubtful integrity of the bladder or gut wall (for example after recent surgery)
- Asthma, latent or active
- Peptic ulcer
- Hyperthyroidism
- Marked bradycardia, low blood pressure, vasomotor instability or coronary disease
- Epilepsy and parkinsonism
Key interactions
- Ganglion-blocking drugs
- Critical fall in blood pressure, usually preceded by severe abdominal symptoms
- Cholinesterase inhibitors (donepezil, galantamine)
- Additive cholinergic effects
- Antimuscarinic drugs
- Opposite effects
What is monitored
- Urine output and post-void residual volume
- Blood pressure and heart rate
- Breathing in people with lung disease
Administration and safety
- Given on an empty stomach to reduce nausea and vomiting
- Obstruction is ruled out before starting
- Atropine is the specific antidote and is kept available
Nursing care
- Have a bedpan or toilet close: urge to void can come quickly
- Measure intake, output and bladder volume
- Watch for flushing, sweating, cramps and dizziness on standing
Pregnancy and breastfeeding
Safety in pregnancy is not established; it is used only if clearly needed.
Test yourself
Think of the answer, then tap the question to see it.
Why does bethanechol last longer than acetylcholine?
It is a choline ester that is not destroyed by cholinesterase.
Which kind of urinary retention can bethanechol treat?
Non-obstructive (functional) retention, for example after surgery or childbirth, or neurogenic atony.
Which respiratory disease is a contraindication to bethanechol?
Asthma, latent or active: muscarinic stimulation causes bronchospasm.
Related drugs
Related conditions
← Back to the class: Muscarinic (cholinergic) agonists
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - BETHANECHOL CHLORIDE tablet (DailyMed (U.S. National Library of Medicine), 2026); Bethanechol: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 11 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.