Ranitidine¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ The H2 antagonists are competitive inhibitors of histamine at the parietal cell H2 receptor. They suppress the normal secretion of acid by parietal cells and the meal-stimulated secretion of acid. They accomplish this by two mechanisms: histamine released by ECL cells in the stomach is blocked from binding on parietal cell H2 receptors which stimulate acid secretion, and other substances that promote acid secretion (such as gastrin and acetylcholine) have a reduced effect on parietal cells when the H2 receptors are blocked. Sucralfate¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ Although sucralfate's mechanism is not entirely understood, there are several factors that most likely contribute to its action. Sucralfate, with its strong negative charge, binds to exposed positively-charged proteins at the base of ulcers. In this way, it coats the ulcer and forms a physical barrier that protects the ulcer surface from further injury by acid and pepsin. It directly inhibits pepsin (an enzyme that breaks apart proteins) in the presence of stomach acid and binds bile salts coming from the liver via the bile thus protecting the stomach lining from injury caused by the bile acids. Sucralfate may increase prostaglandin production, and prostaglandins are known to protect the lining of the stomach and may also bind epithelial growth factor and fibroblast growth factor, both of which enhance the growth and repair mechanism of the stomach lining.
Pharmacology
Ranitidine¿¡ ´ëÇÑ Pharmacology Á¤º¸ Ranitidine is a histamine H2-receptor antagonist similar to cimetidine and famotidine. An H2-receptor antagonist, often shortened to H2 antagonist, is a drug used to block the action of histamine on parietal cells in the stomach, decreasing acid production by these cells. These drugs are used in the treatment of dyspepsia, however their use has waned since the advent of the more effective proton pump inhibitors. Like the H1-antihistamines, the H2 antagonists are inverse agonists rather than true receptor antagonists. Sucralfate¿¡ ´ëÇÑ Pharmacology Á¤º¸ Sucralfate is a prescription medication used to treat peptic ulcers. The current clinical uses of sucralfate are limited. It is effective for the healing of duodenal ulcers, but it is not frequently used for this since more effective drugs (e.g. proton pump inhibitors) have been developed. Although the mechanism of sucralfate's ability to accelerate healing of duodenal ulcers remains to be fully defined, it is known that it exerts its effect through a local, rather than systemic, action. Chemically, sucralfate is a complex of the disaccharide sugar, sucrose, combined with sulfate and aluminum. In acidic solutions (e.g. gastric acid) it forms a thick paste that has a strong negative charge.
Ranitidine¿¡ ´ëÇÑ Absorption Á¤º¸ Approximately 50% bioavailability orally. Sucralfate¿¡ ´ëÇÑ Absorption Á¤º¸ Minimally absorbed from the gastrointestinal tract (up to 5% of the disaccharide component and less than 0.02% of aluminum).
Biotransformation
Ranitidine¿¡ ´ëÇÑ Biotransformation Á¤º¸ Hepatic. Ranitidine is metabolized to the N-oxide, S-oxide, and N-desmethyl metabolites, accounting for approximately 4%, 1%, and 1% of the dose, respectively. Sucralfate¿¡ ´ëÇÑ Biotransformation Á¤º¸ Not Available
Toxicity
Ranitidine¿¡ ´ëÇÑ Toxicity Á¤º¸ LD50=77mg/kg (orally in mice). Symptoms of overdose include muscular tremors, vomiting, and rapid respiration. Sucralfate¿¡ ´ëÇÑ Toxicity Á¤º¸ Acute oral toxicity (LD50) in mice is >8000 mg/kg. There is limited experience in humans with overdosage of sucralfate. Sucralfate is only minimally absorbed from the gastrointestinal tract and thus risks associated with acute overdosage should be minimal. In rare reports describing sucralfate overdose, most patients remained asymptomatic.
Drug Interactions
Ranitidine¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Anisindione The anti-H2 increases the anticoagulant effectDicumarol The anti-H2 increases the anticoagulant effectAcenocoumarol The anti-H2 increases the anticoagulant effectWarfarin The anti-H2 increases the anticoagulant effectItraconazole The anti-H2 decreases the absorption of the imidazoleKetoconazole The anti-H2 decreases the absorption of the imidazoleProcainamide The histamine H2-receptor antagonist increases the effect of procainamideDasatinib Possible decreased levels of dasatinibAtazanavir This gastric pH modifier decreases the levels/effects of atazanaivrTolazoline Anticipated loss of efficacy of tolazoline Sucralfate¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available
Ranitidine¿¡ ´ëÇÑ Food Interaction Á¤º¸ Avoid alcohol.Avoid milk, calcium containing dairy products, iron, antacids, or aluminum salts 2 hours before or 6 hours after using antacids while on this medication.Avoid excessive quantities of coffee or tea (Caffeine).Take without regard to meals. Sucralfate¿¡ ´ëÇÑ Food Interaction Á¤º¸ Avoid alcohol.Take on empty stomach: 1 hour before or 2 hours after meals.Take with a full glass of water.Do not take calcium, aluminum, magnesium or Iron supplements within 2 hours of taking this medication.
Ranitidine¿¡ ´ëÇÑ Description Á¤º¸ A non-imidazole blocker of those histamine receptors that mediate gastric secretion (H2 receptors). It is used to treat gastrointestinal ulcers. [PubChem] Sucralfate¿¡ ´ëÇÑ Description Á¤º¸ A basic aluminum complex of sulfated sucrose. [PubChem]