Bethanechol
Bethanechol stimulates detrusor and gastrointestinal smooth muscle. Veterinary efficacy evidence is limited.
Group
Muscarinic agonist
Mechanism of Action
Directly activates muscarinic receptors and resists acetylcholinesterase hydrolysis.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Urinary bladder atony | 5–15 mg/animal | PO | Every 8 h | Empirical size-related doses: small dogs 2.5 mg, medium dogs 5 mg, large dogs 15 mg. The general range is not a validated weight-band table. |
| Urinary bladder atony | 2.5 mg/animal | PO | Every 8 h | Small-dog alternative. |
| Urinary bladder atony | 5–25 mg/animal | PO | Every 8–12 h | |
| Urinary bladder atony | 2.5–25 mg/animal | PO | Every 8 h | |
| Reduced esophageal sphincter tone | 0.5–1 mg/kg | PO | Every 8 h | |
| Dysautonomia | 1.25–5 mg/animal | PO | Every 24 h | |
| Divided-dose dysautonomia treatment | Reference only | PO | 2.5–7.5 mg total orally divided every 8–12 hours; the passage does not unambiguously distinguish the daily total from the amount per administration. | |
| Dysautonomia | 0.05 mg/kg | SC | Every 12 h | Increase slowly according to response; have atropine available for cholinergic toxicity. |
| Dysautonomia | 1.25–5 mg/animal | PO | Every 12 h |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Urinary bladder atony | 1.25–5 mg/animal | PO | Every 8 h | |
| Urinary bladder atony | 1.25–7.5 mg/animal | PO | Every 8–12 h | |
| Urinary bladder atony | 1.25–7.5 mg/animal | PO | Every 8 h | |
| Dysautonomia | 1.25–5 mg/animal | PO | Every 24 h | |
| Divided-dose dysautonomia treatment | Reference only | PO | 2.5–7.5 mg total orally divided every 8–12 hours; the passage does not unambiguously distinguish the daily total from the amount per administration. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Gastrointestinal motility stimulation | 0.025 mg/kg | SC | Once | Historical regimen; efficacy for gastrointestinal stasis is questionable. |
| Urinary bladder atony | 0.025–0.075 mg/kg | SC | Every 8 h | |
| Urinary bladder atony | 0.25–0.75 mg/kg | PO | Every 6–12 h | Only if weak detrusor contractions remain; dose differs substantially from SC administration. |
| Postoperative bladder atony | 0.4 mg/kg | PO | Every 8–12 h | Foals only; withdraw gradually as bladder function returns. |
Cattle
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Gastrointestinal motility stimulation | 0.07 mg/kg | SC | Once | Historical regimen; efficacy for gastrointestinal stasis is questionable. |
| Cecal dilation without torsion | 0.07 mg/kg | SC | Every 8 h | Up to 2 days; Only for stable or mildly affected cattle still passing feces, without rectal evidence of torsion or retroflexion. Combine fluids and other indicated care; no improvement in 24 hours requires reassessment for surgery. |
Indications
- Urinary bladder atony
- Historical gastrointestinal motility stimulation
Contraindications
- Suspected urinary or gastrointestinal obstruction.
- Compromised bladder integrity, recent gastrointestinal anastomosis, peritonitis, peptic ulceration or inflammatory gastrointestinal lesions.
- Severe bradycardia, hypotension, asthma, epilepsy or hyperthyroidism.
- Hypersensitivity to bethanechol.
Interactions
- Atropine and other anticholinergics oppose its effects.
- Other cholinergic drugs can produce additive cholinergic toxicity.
- Quinidine and procainamide may oppose the response; ganglionic blockers can increase gastrointestinal and hypotensive effects.
Adverse effects
- Abdominal cramping and diarrhea
- Circulatory depression
Toxicity
Cholinergic excess causes salivation, diarrhea, bradycardia, bronchospasm and potentially circulatory collapse. Atropine antagonizes muscarinic toxicity; maintain airway and cardiovascular support.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Bethanechol 5 mg tablet | Tablet | 5 mg / tablet | PO |
| Bethanechol 10 mg tablet | Tablet | 10 mg / tablet | PO |
| Bethanechol 25 mg tablet | Tablet | 25 mg / tablet | PO |
| Bethanechol 50 mg tablet | Tablet | 50 mg / tablet | PO |
| Bethanechol 5 mg/mL injection | Injection | 5 mg / mL | SC |
| Compounded bethanechol chloride 5 mg/mL oral suspension Specific Ora-Plus/Ora-Sweet formulation; 60-day reported potency at 5°C or 25°C protected from light. | Oral Liquid | 5 mg / mL | PO |
Monitoring and Administration
Exclude obstruction before treatment. Monitor urination, gastrointestinal function and cardiovascular response.
Only subcutaneous injection is described. Oral treatment is generally preferred in small animals. Large-animal use for gastrointestinal stasis has uncertain efficacy and is not recommended routinely.
Follow voided volume, bladder size, urination frequency and gastrointestinal tolerance. Exclude mechanical obstruction; increased urethral tone may require a separate outflow-relaxing drug. Give oral doses on an empty stomach unless this is poorly tolerated.
Compounding stability is vehicle-specific: twelve 50 mg tablets in 60 mL Ora-Plus, made to 120 mL with Ora-Sweet or Ora-Sweet SF, gives 5 mg/mL and has reported 60-day potency at 5°C or 25°C protected from light. Do not generalize this to other aqueous vehicles.