bethanechol chloride

Available forms
Available by prescription only
Tablets: 5 mg, 10 mg, 25 mg, 50 mg

Indications and dosages
 Acute postoperative and postpartum nonobstructive (functional) urine retention, neurogenic atony of urinary bladder with retention. Adults: 10 to 50 mg P.O. b.i.d., t.i.d, or q.i.d. When used for urine retention, some patients may require 50 to 100 mg P.O. per dose. Use such doses with extreme caution. Adjust dosage to meet individual requirements.
 Bladder dysfunction caused by phenothiazines ◇. Adults: 50 to 100 mg P.O. q.i.d.
 To lessen the adverse effects of tricyclic antidepressants ◇. Adults: 25 mg P.O. t.i.d.
 Chronic gastric reflux ◇. Adults: 25 mg P.O. q.i.d.
Children: 3 mg/m²/dose P.O. t.i.d.

Pharmacodynamics
Urinary tract stimulant action: Bethanechol directly binds to and stimulates muscarinic receptors of the parasympathetic nervous system. This increases tone of the bladder detrusor muscle, usually resulting in contraction, decreased bladder capacity, and subsequent urination.
GI tract stimulant action: Bethanechol directly stimulates cholinergic receptors, leading to increased gastric tone and motility and peristalsis. Drug improves lower esophageal sphincter tone by directly stimulating cholinergic receptors, thereby alleviating gastric reflux.

Pharmacokinetics
Absorption: Poorly absorbed from the GI tract (absorption varies considerably among patients).
Distribution: Largely unknown; however, therapeutic doses don’t penetrate the blood-brain barrier.
Metabolism: Unknown.
Excretion: Unknown.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug or its components. Also contraindicated in patients with uncertain strength or integrity of the bladder wall, mechanical obstructions of the GI or urinary tract, hyperthyroidism, peptic ulceration, latent or active bronchial asthma, pronounced bradycardia or hypotension, vasomotor instability, cardiac or coronary artery disease, seizure disorder, Parkinson’s disease, spastic GI disturbances, acute inflammatory lesions of the GI tract, peritonitis, or marked vagotonia. Also contraindicated when increased muscular activity of GI or urinary tract is harmful. Use cautiously in pregnant women.

Interactions
Drug-drug. Cholinergic drugs, especially cholinesterase inhibitors: Additive effects may occur. Avoid use together.
Ganglionic blockers such as mecamylamine: May cause critical blood pressure decrease; this effect is usually preceded by abdominal symptoms. Avoid use together.
Procainamide, quinidine: May reverse cholinergic effect of bethanechol on muscle. Monitor patient for clinical effect.

Adverse reactions
CNS: headache, malaise.
CV: flushing, hypotension, reflex tachycardia.
EENT: lacrimation, miosis.
GI: abdominal cramps, diarrhea, excessive salivation, nausea, belching, borborygmi.
GU: urinary urgency.
Hepatic: liver dysfunction.
Respiratory: bronchoconstriction, increased bronchial secretions.
Skin: diaphoresis.

Effects on lab test results
• May increase AST, bilirubin, amylase, and lipase levels.

Overdose and treatment
Signs and symptoms of overdose include nausea, vomiting, abdominal cramps, diarrhea, involuntary defecation, urinary urgency, excessive salivation, miosis, excessive tearing, bronchospasm, increased bronchial secretions, hypotension, excessive sweating, bradycardia or reflex tachycardia, and substernal pain.
 Treatment requires discontinuation of drug and administration of atropine by S.C., I.M., or I.V. route. (Atropine must be administered cautiously; an overdose could cause bronchial plug formation.) Contact local or regional poison control center for more information.

Special considerations
• Atropine sulfate should be readily available to counteract toxic reactions that may occur during treatment with bethanechol.
• For administration to treat urine retention, bedpan should be readily available.
• Give drug on an empty stomach; eating soon after drug administration may cause nausea and vomiting.
• Monitor blood pressure; patients with hypertension receiving bethanechol may experience a precipitous decrease in blood pressure.
• Store drug in tight container between 59° and 86° F (15° and 30° C). Avoid freezing.
Pregnant patients
• Bethanechol shouldn’t be used in pregnant women.
Pediatric patients
• Safety and efficacy haven’t been established in children.

Patient education
• Instruct patient to take oral form on an empty stomach and at regular intervals.
• Inform patient that drug is usually effective within 30 to 90 minutes after oral administration.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use