Histamine H2 receptor antagonists ranitidine

The bioslurry treatment successfully removed several of the PhC to non-detectable levels after 26 days three histamine H2-receptor antagonists (ranitidine, famotidine, cimetidine), two (1-blockers (atenolol, sotalol), one barbiturate (butalbital) and one antidiabetic compound (glibenclamide). The elimination of the sulfonamide antibiotics sulfapyridine (100%), sulfamethazine (91.0%) and... 

The following amides prepared from 4-(3-nitro-l-pyrazolyl)butanoic acid, CDI, and primary amines represent partial structures of the histamine H2-receptor antagonists roxatidine, cimetidine, ranitidine, and famotidine [37]... 

Histamine H2-receptor antagonists are well absorbed orally, although concurrent antacid therapy may reduce bioavailability by up to 30%. They are widely distributed in the body, crossing the blood-brain barrier and the placenta. Cimetidine, ranitidine and famotidine are extensively metabolised in the liver, and about one-third excreted unchanged in urine, while only one-third of nizatidine is metabolised (Table 11.1). Elimination half-life is increased up to tenfold in renal failure, and doses must be adjusted. 

Histamine H2-receptor antagonists are the mainstay of prevention of Mendelson s syndrome at present. Probably the best protection is afforded by a combination of H2-receptor blockade by ranitidine and a single oral dose of sodium citrate or bicarbonate. Because of its longer duration of action, and relative lack of enzyme inhibition, ranitidine is preferred to cimetidine for this purpose, although there is a latent period of 1-2 hours before it takes effect. Famotidine and nizatidine are probably equally effective in blocking acid secretion. 

Actions The histamine H2-receptor antagonists—cimetidine, ranitidine, famotidine, and nizatidine—act on H2-receptors in the stomach, blood vessels, and other sites. They are competitive antagonists of histamine and are fully reversible. These agents completely inhibit gastric acid secretion induced by histamine, or gastrin. However, they only partially inhibit gastric acid secretion induced by acetylcholine or bethanechol. 

Ranitidine (Zantac /GlaxoSmithKline) is a histamine H2-receptor antagonist that inhibits the release of gastric acid and is useful in the treatment of a variety of hypersecretory conditions [dyspepsia, heartburn, duodenal and gastric ulcers, and gastroesophageal reflux (GERD)]. Lansoprazole (Prevacid /TAP), omeprazole (Prilosec /AstraZeneca), and esomeprazole (Nexium /AstraZeneca) are benzimidazole... 

The metabolism of lorazepam (e.g., Ativan), oxazepam (e.g., Serax), and temazepam (e.g., Restoril) are not likely to be affected, and one of these agents may be preferred when a benzodiazepine is indicated in a patient being treated with cimetidine. The experience with ranitidine (e.g., Zantac), famotidine (Pepcid), and nizatidine (Axid) suggests that these agents are not likely to inhibit hepatic enzyme systems, and these other histamine H2-receptor antagonists are less likely than cimetidine to interact with other drugs that are metabolized via these pathways. 

The available data on a possible interaction between histamine H2 receptor antagonists and ciclosporin are inconclusive. Whereas neither cimetidine nor ranitidine significantly altered ciclosporin pharmacokinetics, there was an increase in serum creatinine concentration in patients taking both ciclosporin and cimetidine, but not ranitidine. The clinical significance of this interaction is probably limited, and it has been attributed to competition of cimetidine with creatinine for tubular secretion (251). 

Histamine H2-receptor antagonists inhibit acid secretion by blocking the stimulation of H2-receptors in the gastric parietal cell. They are Cimetidine Nizatidine Ranitidine Roxatidine... 

Tracqui, A. Kintz, P. Mangin, P Lugnier, AA. Chaumont, A.J. A new rapid HPLC assay for the simultaneous determination of two histamine H2-receptor antagonists, cimetidine and ranitidine, in human plasma. J.Toxicol.Clin.Exp., 1988, 8, 387-394 [LOD 25 ng/mL plasma]... 

Kirch W, Ramsch K, Janisch HD, Ohnhaus EE. The influence of two histamine H2-receptor antagonists, cimetidine and ranitidine, on plasma levels and clinical effect of nifedipine and metoprolol. Arch Toxicol (1984) (Siq)pl 7), 256-9. 

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