Homatropine methyl bromide is a synthetic anticholinergic drug that works by blocking the action of acetylcholine on smooth muscles. It is commonly used to relieve gastrointestinal spasms and cramps, including those of the stomach and intestines. The drug also has anti secretory properties, reducing excessive secretions in the digestive tract. Chemically, it is a quaternary ammonium compound, which limits its ability to cross the blood-brain barrier, reducing central nervous system effects. Homatropine methyl bromide is often administered orally or by injection. It is used in conditions like irritable bowel syndrome, peptic ulcers, and biliary colic. The drug works by relaxing smooth musclesand decreasing motility. Its effects are short-acting, so it may need repeated dosing. Common side effects are related to dry mouth, blurred vision, and urinary retention. Homatropine methyl bromide is preferred over some other anti cholinergics for peripheral effects without significant CNS involvement.
BRAND NAMES
Homatropine Methylbromide is marketed under various brand names depending on the country and formulation. Common brands include Homatropine Bromide, Homatropine MB, and some combination products with antispasmodics. It is available in tablet and injectable forms for clinical use. These products are mainly used for gastrointestinal spasms, abdominal pain, or as a pre-anesthetic agent. Brand availability may vary by region.
MCHANISM OF ACTION
Homatropine Methylbromide is an anticholinergic drug that blocks muscarinic acetylcholine receptors. By inhibiting parasympathetic stimulation, it reduces smooth muscle spasms in the gastrointestinal and urinary tracts. It also decreases secretions in the stomach and respiratory tract. The drug produces mild mydriasis when used in ophthalmology. Its primary effect is relaxation of smooth muscles and reduction of secretions.
PHARMACOKINETICS
Absorption
Homatropine Methylbromide is absorbed moderately from the gastrointestinal tract after oral administration. Peak plasma concentrations are usually reached within 30–60 minutes. Bioavailability is affected by first-pass metabolism in the liver. Absorption is more rapid when given parenterally. Overall, the drug achieves sufficient systemic levels for clinical effect.
Distribution
The drug is widely distributed in body tissues, particularly smooth muscles. It crosses membranes poorly due to its quaternary ammonium structure, limiting central nervous system penetration. It binds partially to plasma proteins. Distribution ensures that target organs, such as the gut and urinary tract, are reached effectively. Volume of distribution is moderate.
Metabolism
Homatropine Methylbromide undergoes partial hepatic metabolism. The extent of metabolism is limited, with most of the drug remaining unchanged in plasma. Metabolites are usually inactive. Liver function can influence the rate of drug metabolism. Metabolic activity contributes minimally to therapeutic effect.
Excretion
Excretion occurs mainly through the urine. A small amount may be eliminated in feces. Renal function significantly affects clearance. Most of the drug and its metabolites are removed within 24 hours. Accumulation is uncommon in patients with normal kidney function.
PHARMACODYNAMICS
Homatropine Methylbromide reduces smooth muscle spasms by blocking muscarinic receptors. It also decreases secretions in the gastrointestinal and respiratory tracts. The drug produces mild mydriasis and cycloplegia in the eyes. Onset of action is rapid after parenteral use. Its effects are primarily peripheral with minimal central nervous system impact.
ADMINISTRATION
Homatropine Methylbromide can be administered orally or via injection. Oral tablets are typically used for gastrointestinal spasms. Injectable forms are used for faster action or in hospital settings. The drug should be taken with water and according to prescribed intervals. Dosing should be individualized based on the severity of symptoms.
DOSAGE AND STRENGTH
Typical oral tablets contain 0.2–0.4 mg per dose. Injectable forms usually contain 0.2–0.5 mg per mL. The dose is adjusted according to the patient’s age, weight, and clinical condition. Usually taken 2–3 times daily for adults. Maximum daily dose should not be exceeded to prevent anticholinergic side effects.
DRUG INTERACTIONS
May have additive effects with other anticholinergic drugs, increasing risk of dry mouth, tachycardia, or urinary retention.
Can reduce the effect of cholinesterase inhibitors used in myasthenia gravis.
Use with antihistamines or tricyclic antidepressants may enhance side effects.
May interact with drugs affecting gastrointestinal motility.
Careful monitoring is required when combined with multiple CNS-acting agents.
FOOD INTERACTIONS
Food has minimal effect on drug absorption.
Oral administration with a small meal may reduce gastrointestinal irritation.
High-fat meals may slightly delay absorption.
No specific dietary restrictions are required.
Patients can continue normal diet during treatment.
CONTRAINDICATIONS
Known hypersensitivity to Homatropine Methylbromide.
Glaucoma, especially narrow-angle glaucoma.
Severe cardiac arrhythmias or tachycardia.
Myasthenia gravis due to worsening muscle weakness.
Obstructive urinary or gastrointestinal disorders like pyloric stenosis.
SIDE EFFECTS
Dry mouth, thirst, and decreased sweating.
Blurred vision or mild mydriasis.
Tachycardia or palpitations.
Constipation or urinary retention.
Rare allergic reactions like rash or itching.
OVER DOSE
Overdose may lead to severe anticholinergic effects. Symptoms include extreme dry mouth, blurred vision, tachycardia, confusion, and urinary retention. Severe cases can cause hallucinations or seizures. Treatment involves supportive care, activated charcoal, and monitoring of vitals. Symptomatic management is essential for recovery.
TOXICITY
Homatropine Methylbromide is generally low in toxicity at therapeutic doses. Toxic effects are primarily anticholinergic in nature. Overdose or accumulation in renal impairment can cause serious complications. Monitoring kidney and heart function reduces risk. The drug is safe when used as prescribed and monitored by healthcare professionals.
