Magstop

Uses

Famotidine is used for-

• Short term treatment of active duodenal ulcer and benign gastric ulcer
• Maintenance therapy for prevention of relapses of duodenal ulceration
• Gastro-oesophageal reflux disease
• Zollinger Ellison Syndrome

Magstop is also used to associated treatment for these conditions: Chronic Back Pain, Duodenal Ulcer, Erosive Esophagitis, Extra-Articular Rheumatism, Gastritis, Heartburn, Helicobacter Pylori Infection, Multiple Endocrine Neoplasia, Muscle Spasms, Nonspecific Pain Post Traumatic Injury, Osteoarthritis (OA), Postoperative pain, Stress Ulcers, Zollinger-Ellison Syndrome, Active Gastric ulcer, Acute Duodenal Ulcers, Gastrointestinal ulceration, Pathological hypersecretory conditions, Symptomatic non-erosive gastroesphageal reflux disease

How Magstop works

Histamine acts as a local hormone that stimulates the acid output by parietal cells via a paracrine mechanism. Neuroendocrine cells called enterochromaffin-like (ECL) cells lie close to the parietal cells and regulate the basal secretion of histamine. Histamine release is also promoted from stimulation by acetylcholine and gastrin, a peptide hormone. Gastrin (G) cells release gastrin, which works on CCK₂ receptors on ECL cells. This action promotes the release of histamine from ECL cells. Upon release, histamine acts on H₂ receptors expressed on the basolateral membrane of parietal cells, leading to increased intracellular cAMP levels and activated proton pumps on parietal cells. Proton pump releases more protons into the stomach, thereby increasing the secretion of acid. In conditions that are associated with acid hypersecretion such as ulcers, there is a loss of regulation of acid secretion. Famotidine works on H₂ receptors and blocks the actions of histamine.

Dosage

Magstop dosage

Duodenal ulcer: 40 mg at night for 4 to 8 weeks

Benign gastric ulcer: 40 mg at night for 4 to 8 weeks; Maintenance therapy: 20 mg at night for preventing the recurrences of duodenal ulceration

Gastro-oesophageal reflux disease: 20 mg twice daily for 6 to 12 weeks

Zollinger Ellison syndrome: The recommended starting dose is 20 mg every six hours. Dosage should then be adjusted to individual response. Doses up to 160 mg every six hours have been administered to some patients without the development of significant adverse effects.

Dosage can be administered irrespective of meals. Antacids may be given concomitantly if needed.

Side Effects

Famotidine is generally well tolerated and side effects are uncommon. Dizziness, headache, constipation and diarrhoea have been reported rarely. Other side effects reported less frequently include dry mouth, nausea and/or vomiting, rash, abdominal discomfort, anorexia and fatigue.

Toxicity

The oral LD₅₀ is 4049 mg/kg in rats and 4686 mg/kg in mice. The subcutaneous LD₅₀ is 800 mg/kg in rats and mice. The lowest published toxic dose (TDLo) in man following oral administration is 4 mg/kg/7D.

Symptoms of overdose resemble the adverse events seen with the use of recommended doses, and they should be responded with supportive and symptomatic treatment. Any unabsorbed drug should be removed from the gastrointestinal tract, and the patient should be monitored accordingly. The use of hemodialysis to eliminate the drug from the systemic circulation is effective, but the experience of using hemodialysis in response to famotidine overdose is limited in clinical settings.

Precaution

Dosage reduction should be considered or interval between doses should be prolonged if creatinine clearance falls to or below 30 ml/min.

Interaction

Famotidine does not interact with the cytochrome P450 linked drug metabolising enzyme system. So, no interactions have been found in man with Warfarin, Theophylline, Phenytoin, Diazepam, Propranolol, Aminopyrine or antipyrine.

Volume of Distribution

The steady-state volume of distribution ranges from 1.0 to 1.3 L/kg. Famotidine is found in breast milk; however, it is found in breast milk at the lowest concentrations compared to other H₂ receptor antagonists.

Elimination Route

Following oral administration, the absorption of famotidine is dose-dependent and incomplete. The oral bioavailability ranges from 40-50%, and the Cmax is reached in 1-4 hours post-dosing. While the bioavailability can be slightly increased with the intake of food and decreased by antacids, there is no clinical significance.

Half Life

The elimination half-life is about 2 to 4 hours. The half-life is expected to increase nonlinearly in patients with decreased renal function.

Clearance

Renal clearance is 250-450 mL/min, indicating some tubular excretion. Because the renal clearance rate exceeds the glomerular filtration rate, famotidine is thought to be mainly eliminated via both glomerular filtration and renal tubular secretion.

Elimination Route

About 65-70% of the total administered dose of famotidine undergoes renal elimination, and 30-35% of the dose is cleared by metabolism. Following intravenous administration, about 70% of the drug is eliminated in the urine as an unchanged drug.

Pregnancy & Breastfeeding use

Pregnancy: There are no adequate, well controlled studies on Famotidine in pregnancy, but it is known to cross the placenta and should be prescribed only if clearly needed.

Lactation: It is not known whether Famotidine is secreted into human milk, nursing mothers should either stop nursing or stop taking the drug.

Contraindication

There are no known contraindication to Famotidine. If any evidence of hypersensitivity appear, the therapy should be discontinued and consultation with physician is required.

Storage Condition

Tablet: Store between 15-30° C. Concentrate for injection: Store between 2-8° C.

Innovators Monograph

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