Usage
Bethanechol is prescribed for the treatment of urinary retention (difficulty urinating) that may occur postoperatively, postpartum, or due to neurogenic bladder atony. It belongs to the pharmacological classification of cholinergic agonists or parasympathomimetics, specifically a muscarinic agonist. It mimics the action of acetylcholine at muscarinic receptors. This action stimulates detrusor muscle contraction and bladder emptying. Bethanechol increases the tone of the detrusor urinae muscle, facilitating bladder emptying.
Alternate Names
Bethanechol is also known as bethanechol chloride. Brand names include Urecholine, Duvoid, and Myotonachol.
How It Works
Pharmacodynamics: Bethanechol primarily stimulates muscarinic cholinergic receptors in the urinary and gastrointestinal tracts. This results in increased detrusor muscle tone and contractions, facilitating bladder emptying. In the GI tract, it increases motility and secretions.
Pharmacokinetics:
- Absorption: Well-absorbed orally, though less effectively than by subcutaneous administration. Taking it on an empty stomach enhances absorption.
- Metabolism: Minimal hepatic metabolism. It is not metabolized by CYP enzymes.
- Elimination: Primarily excreted unchanged in the urine.
Mode of Action: Bethanechol binds directly to muscarinic cholinergic receptors (M2 and M3 subtypes) on the detrusor muscle of the bladder, activating them. This leads to increased phosphoinositide turnover, release of intracellular calcium, and ultimately smooth muscle contraction, causing bladder emptying. It does not inhibit acetylcholinesterase.
Elimination Pathways: Primarily renal excretion.
Dosage
Standard Dosage
Adults:
- Oral: 10-50 mg three or four times a day. The initial dose is 5–10 mg, which can be repeated hourly until a satisfactory response or up to a maximum single dose of 50 mg.
- Subcutaneous: 2.5–5 mg three or four times daily. It is crucial to administer bethanechol subcutaneously; intravenous or intramuscular routes are contraindicated due to potential serious adverse effects.
Children:
- Oral: 0.3–0.6 mg/kg/day divided three to four times a day. It is generally recommended to administer the dose 1 hour before or 2 hours after meals to minimize gastrointestinal upset. Maximum dose is 0.4 mg/kg or 10 mg per dose. Safety and efficacy have not been fully established in the pediatric population. It is typically given for GERD treatment or for cases of urinary retention. The use of bethanechol in pediatrics is considered off-label in some cases.
Special Cases:
- Elderly Patients: Start with a lower dose and titrate cautiously, monitoring for side effects.
- Patients with Renal Impairment: No specific dosage adjustments are indicated in the manufacturer’s labeling.
- Patients with Hepatic Dysfunction: No specific dosage adjustments are indicated in the manufacturer’s labeling, although the metabolic disposition of bethanechol is not fully understood.
- Patients with Comorbid Conditions: Use with caution in patients with asthma, peptic ulcer disease, hyperthyroidism, hypotension, bradycardia, coronary artery disease, epilepsy, Parkinsonism, and recent bladder surgery.
Clinical Use Cases
Bethanechol does not have approved or recommended dosages for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. It is primarily used for urinary retention.
Dosage Adjustments
Dosage adjustments might be needed in patients with pre-existing conditions or taking interacting medications.
Side Effects
Common Side Effects
- Abdominal cramps/pain
- Nausea
- Vomiting
- Diarrhea
- Increased salivation
- Increased urination
- Flushing
- Sweating
- Headache
- Dizziness
- Malaise
Rare but Serious Side Effects
- Hypotension
- Bradycardia
- Bronchospasm/asthmatic attacks
- Seizures (rare)
Long-Term Effects
No specific long-term side effects have been identified, but prolonged use may exacerbate underlying conditions like peptic ulcers or asthma.
Adverse Drug Reactions (ADR)
Clinically significant ADRs include severe hypotension, bronchospasm, and allergic reactions.
Contraindications
- Hypersensitivity to bethanechol
- Hyperthyroidism
- Peptic ulcer
- Asthma (active or latent)
- Bradycardia
- Hypotension
- Coronary artery disease
- Epilepsy
- Parkinsonism
- Gastrointestinal or urinary tract obstruction
- Recent urinary bladder surgery
Drug Interactions
- Anticholinergics: Antagonistic effects (e.g., atropine, diphenhydramine).
- Cholinesterase inhibitors: Additive cholinergic effects (e.g., donepezil, galantamine).
- Beta-blockers: Increased risk of bradycardia and hypotension.
- Procainamide, quinidine: May enhance cholinergic effects.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C (animal studies show adverse effects, but there are no adequate and well-controlled studies in pregnant women). Use only if clearly needed, weighing the potential benefits against the potential risks.
- Breastfeeding: Unknown if excreted in breast milk. Use with caution and monitor infants for cholinergic effects (diarrhea, increased tearing, excessive salivation, or urination).
Drug Profile Summary
- Mechanism of Action: Muscarinic cholinergic receptor agonist.
- Side Effects: Abdominal cramps, nausea, vomiting, diarrhea, increased salivation/urination, flushing, sweating, headache, dizziness. Rarely: hypotension, bronchospasm, seizures.
- Contraindications: Hypersensitivity, hyperthyroidism, peptic ulcer, asthma, bradycardia, hypotension, CAD, epilepsy, parkinsonism, GI/GU obstruction, recent bladder surgery.
- Drug Interactions: Anticholinergics, cholinesterase inhibitors, beta-blockers.
- Pregnancy & Breastfeeding: Category C; use with caution. Excretion in breast milk unknown.
- Dosage: Adults: 10–50 mg PO TID/QID or 2.5-5 mg SC TID/QID. Pediatrics: 0.3-0.6 mg/kg/day divided TID/QID (off-label).
- Monitoring Parameters: Blood pressure, heart rate, respiratory status, urinary output.
Popular Combinations
Bethanechol is not typically used in combination with other medications, and no specific drug combinations are recommended in standard clinical practice.
Precautions
- General Precautions: Assess for allergies, contraindications, and potential drug interactions before initiating therapy.
- Specific Populations: Caution in elderly, pregnant/breastfeeding women, and children.
- Lifestyle Considerations: Avoid alcohol due to increased risk of drowsiness.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Bethanechol?
A: Adults: 10-50 mg PO TID/QID, children: 0.3–0.6 mg/kg/day divided TID/QID (off-label).
Q2: How should Bethanechol be administered?
A: Orally or subcutaneously. Never administer intravenously or intramuscularly. Administer oral doses on an empty stomach.
Q3: What is the mechanism of action of Bethanechol?
A: Directly stimulates muscarinic cholinergic receptors in the bladder, leading to detrusor muscle contraction and bladder emptying.
Q4: What are the common side effects of Bethanechol?
A: Abdominal cramps, nausea, vomiting, diarrhea, increased salivation, flushing, sweating.
Q5: What are the contraindications to using Bethanechol?
A: Hypersensitivity, hyperthyroidism, peptic ulcer, asthma, bradycardia, hypotension, coronary artery disease, epilepsy, Parkinsonism, and GI/GU obstruction.
Q6: Can Bethanechol be used during pregnancy or breastfeeding?
A: Use with caution during pregnancy (Category C). Its presence in breast milk is unknown; monitor infants for cholinergic side effects.
Q7: What are the signs of Bethanechol overdose?
A: Abdominal discomfort, salivation, flushing, sweating, nausea, vomiting. Atropine is the antidote.
Q8: Does Bethanechol interact with other medications?
A: Yes, it can interact with anticholinergics, cholinesterase inhibitors, and beta-blockers. Provide a complete medication history for assessment of potential interactions.
Q9: What should patients be advised regarding Bethanechol administration?
A: Take on an empty stomach to reduce nausea and vomiting. Report any severe or persistent side effects. Avoid activities requiring alertness until the effects of the drug are known.
