Muscarinic Agonist
Pregnancy: C
Bethanechol
Brand names: Myotonine
Adult dose
Dose: 10–25 mg three to four times daily
Route: oral
Frequency: three to four times daily
Max: 100 mg/day
Take 30 minutes before meals; used for urinary retention with underactive detrusor; seldom used due to side effects and limited efficacy
Paediatric dose
Dose: 0.6 mg/kg
Route: oral
Frequency: three times daily
Max: 25 mg three times daily
Rarely used in paediatrics; specialist use only
Dose adjustments
Renal
Use with caution
Hepatic
Use with caution
Paediatric weight-based calculator
Rarely used in paediatrics; specialist use only
Clinical pearls
- Cholinomimetic — stimulates bladder detrusor directly
- Not absorbed if given sublingually; oral bioavailability variable
- Largely superseded by intermittent self-catheterisation for underactive bladder
Contraindications
- Urinary obstruction
- Intestinal obstruction
- Hyperthyroidism
- Asthma/COPD
- Bradycardia
- Hypotension
- Recent GI surgery
Side effects
- Abdominal cramps
- Diarrhoea
- Nausea
- Bradycardia
- Hypotension
- Bronchoconstriction
- Salivation
- Flushing
Interactions
- Beta-blockers (bradycardia)
- Anticholinesterases (enhanced muscarinic effects)
- Antihypertensives (hypotension)
Monitoring
- Blood pressure
- Heart rate
- Urinary symptoms
Reference: BNFc; BNF 86. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.