Bethanechol
A synthetic choline ester that activates muscarinic receptors, used to help the bladder empty in urinary retention.
Drug card
- How it works
- Activating muscarinic receptors, so glands secrete and smooth muscle contracts
- Used for
- Urinary retention after surgery or childbirth
- Neurogenic bladder that does not empty
- Known for
- Abdominal cramps and colicky pain
- Asthma attacks and airway narrowing
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does bethanechol work?
A synthetic ester related to acetylcholine that acts on muscarinic receptors with little nicotinic effect. It contracts the detrusor muscle so the bladder empties, and raises gut tone and motility. Cholinesterase does not break it down, so it outlasts acetylcholine, and its charged quaternary structure keeps it out of the brain.
Like other direct-acting muscarinic agonists: They bind to muscarinic acetylcholine receptors and switch them on, copying the parasympathetic nervous system. Glands then secrete more saliva, sweat and tears, the bladder's detrusor and the gut wall contract, the pupil narrows and the heart can slow. Bethanechol, a choline ester, is not broken down by cholinesterase, so it acts for longer than acetylcholine.
Uses
What is bethanechol used for?
- Urinary retention after surgery or childbirth
- Neurogenic bladder that does not empty
Side effects
Side effects of bethanechol
- Abdominal cramps and colicky painKnown for
- Asthma attacks and airway narrowingKnown forSerious
- Diarrhea
- Excess saliva
- Sweating
- Flushing with a feeling of heat
- Urinary urgency
- Nausea and belching
- Headache
- Fall in blood pressure with a fast pulse
- Watery eyes
- Small pupils (miosis)
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated in asthma, peptic ulcer, hyperthyroidism, epilepsy and parkinsonism.
- Never used when the bladder or gut is blocked, or its wall is weak, as after recent bladder or bowel surgery.
- Contraindicated with marked bradycardia, low blood pressure or coronary artery disease.
- With ganglion-blocking drugs, blood pressure can fall to a dangerous level.
Good to know: Resists cholinesterase, unlike acetylcholine, so its effect lasts; atropine is the specific antidote when too much is given.
Remember it
A way to remember it
SLUDGE
- S
- Salivation
- L
- Lacrimation (watery eyes)
- U
- Urination (urgency and frequency)
- D
- Defecation (diarrhea)
- G
- GI cramps
- E
- Emesis (vomiting)
A mnemonic widely used in teaching
Its class
Direct-acting muscarinic agonists
Other direct-acting muscarinic agonists with a card:
Easily mixed up with anticholinesterases and antimuscarinics.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Autonomic nervous system
Bethanechol is one of 10 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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