Valethamate bromide is a synthetic anticholinergic and antispasmodic agent, structurally related to atropine. It acts as a competitive antagonist at muscarinic acetylcholine receptors (M1, M2, M3), leading to smooth muscle relaxation, particularly in the gastrointestinal and genitourinary tracts. In the Indian clinical context, it is primarily used for its potent spasmolytic effects to relieve pain associated with smooth muscle spasms, such as in renal colic, biliary colic, and dysmenorrhea. Its use has declined with the advent of more selective agents but remains a relevant option in specific scenarios.
Adult: Oral: 8mg to 16mg, three to four times daily. Intramuscular: 8mg to 16mg, repeated every 4-6 hours as needed for acute spasm. The 8mg tablet is a common single dose.
Note: Oral tablets should be taken with a full glass of water, with or without food. For acute colic, it is often administered intramuscularly in a clinical setting. Do not crush or chew unless advised. The duration of therapy should be limited to the acute symptomatic phase.
Valethamate bromide competitively and reversibly blocks the action of acetylcholine at postganglionic muscarinic receptors (M1, M2, M3) in smooth muscle, exocrine glands, and the cardiac conduction system. This blockade inhibits parasympathetic nerve impulses, leading to relaxation of smooth muscle in organs like the gastrointestinal tract, biliary system, ureters, and uterus. It also reduces glandular secretions.
Pregnancy: Category C: Animal reproduction studies have not been conducted. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus. Should be avoided, especially in the first trimester, unless absolutely necessary for severe colic.
Driving: May cause dizziness, drowsiness, and blurred vision. Patients should be cautioned against driving or operating machinery if they experience these effects.
| Other Anticholinergics (e.g., Atropine, Dicyclomine, Oxybutynin, Tricyclic Antidepressants, Antihistamines) | Additive anticholinergic effects leading to increased side effects (dry mouth, constipation, urinary retention, confusion). | Major |
| Potassium Chloride (wax-matrix formulations) | Increased risk of gastrointestinal mucosal lesions or ulceration due to reduced GI motility. | Moderate |
| Metoclopramide, Domperidone | Pharmacological antagonism; Valethamate reduces GI motility, counteracting the prokinetic effect. | Moderate |
| Digoxin | Increased bioavailability of digoxin due to reduced GI motility, potentially leading to toxicity. | Moderate |
| Levodopa | Reduced absorption of levodopa from the GI tract, potentially decreasing its efficacy. | Moderate |
| Alcohol, CNS Depressants (Benzodiazepines, Opioids) | Additive sedative effects, increased drowsiness and impaired psychomotor performance. | Moderate |
| Amantadine | Enhanced anticholinergic side effects. | Moderate |
Same composition (Valethamate (8mg)), different brands: