Bethanechol Side Effects
Bethanechol produces adverse effects through direct muscarinic receptor activation throughout the body, causing overstimulation of muscarinic receptors in smooth muscle, cardiac muscle, and secretory glands, with side effects being more common following subcutaneous injection than oral administration. 1, 2
Cardiovascular Effects
- Bradycardia occurs through direct muscarinic stimulation of cardiac tissue 1
- Hypotension with reflex tachycardia can develop as a vasomotor response 2
- Flushing producing warmth sensation, particularly about the face 2
Gastrointestinal Effects
- Abdominal cramps or discomfort and colicky pain are common 2
- Nausea, belching, and diarrhea occur due to increased GI motility 2
- Excessive salivation from muscarinic effects on secretory glands 1, 2
- Borborygmi (intestinal rumbling sounds) 2
Respiratory Effects
- Bronchial constriction and potential asthmatic attacks can occur in susceptible individuals, particularly concerning in patients with underlying reactive airway disease 1, 2
Genitourinary Effects
- Urinary urgency develops from increased bladder smooth muscle contraction 2
- This contrasts with anticholinergic toxicity which causes urinary retention 1
Dermatologic Effects
- Excessive sweating due to muscarinic effects on secretory glands 1, 2
- This contrasts with anticholinergic toxicity which causes hot, dry skin 1
Ophthalmic Effects
Neurologic Effects
- Headache 2
- Malaise 2
- Seizures have been reported, though a causal relationship has not been established 2
Important Clinical Distinctions
- Bethanechol produces the opposite effects of anticholinergic toxicity: it causes sweating (not dry skin) and urinary urgency (not retention), which is clinically important when bethanechol is used to counteract anticholinergic side effects of other medications like tricyclic antidepressants 1, 3