Famotidine, histamine antagonists

The discovery and development of cimetidine and ranitidine provided a revolution in the medical treatment and management of peptic ulcer disease. Subsequently, many pharmaceutical companies became involved in research programs to discover additional compounds as H2-receptor histamine antagonists. As a result, a very wide range of chemical structures now exists for this class of drug (for a review, see Cooper et al. [19]). Many of these compounds have been investigated in human studies, but only the above-mentioned five drugs - cimetidine, ranitidine, nizatidine, famotidine, and roxatidine - are marketed as medicines. 

Histamine 10 6 g/ml Histamine antagonists, e.g. cimetidine, ranitidine, famotidine... 

The client with partial- and full-thickness burns to 35% of the body is admitted to the burn department. The HCP has prescribed famotidine (Pepcid), a histamine antagonist. Which statement best describes the scientific rationale for administering this medication ... 

From 1981 to 1995 other dmgs switched to OTC were the antifiingal preparations containing micona2ole nitrate [22832-87-7] (7) and clotrima2ole [23593-75-1] (8) the antiinflammatory agent ibuprofen [15687-27-1] (9) and the histamine H2-receptor antagonists famotidine [76824-35-6] (10) and cimetidine [51481-61-9] (11). 

These drug inhibit die action of histamine at histamine H2 receptor cells of die stomach, which then reduces die secretion of gastric acid and reduces total pepsin output. The decrease in acid allows the ulcerated areas to heal. Examples of histamine H2 antagonists include cimetidine (Tagamet), famotidine (Pepcid), nizatidine (Axid Pulvules), ranitidine (Zantac). 

HISTAMINE H2 ANTAGONISTS. The nurse administers ranitidine and oral cimetidine before or with meals and at bedtime Nizatidine and famotidine are given at bedtime or, if twice-a-day dosing is prescribed, in the morning and at bedtime. These drugp are usually given concurrently with an antacid to relieve the pain. In certain situations or disorders, cimetidine and ranitidine may also be given by intermittent IV infusion or direct IV injection. 

Intravenous histamine-2-receptor antagonists such as ranitidine, famotidine, and cimetidine are compatible with PN and can be added to the daily PN for prevention of stress-related mucosal damage and peptic ulcer disease. This provides a continuous acid suppression and reduces nursing time by avoiding intermittent scheduled infusions. 

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]... 

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... 

Histamine-2 antagonists (cimetidine, famotidine, nizatidine, ranitidine) may be used in low doses to manage simple nausea and vomiting associated with heartburn or gastroesophageal reflux. 

Reflux is generally treated with lifestyle modifications followed by acid suppression in the form of histamine-2 receptor antagonists (e.g., ranitidine, famotidine) or PPIs, which are more efficacious (7-10). 

Traditional or Hj antihistamine drugs block many effects caused by histamine however, it turns out that they are not able to withstand events mediated by H2 receptors, in particular excess gastric juice secretion. In 1977 an H2-receptor antagonist, cimetidine, was proposed, which revolutionized stomach ulcer treatment. Later on, ranitidine was proposed, followed by drugs with minor structural and pharmacological differences such as famotidine and nizatidine. 

As discussed earlier, receptors are responsible for histamine induced gastric acid secretion. H -receptors antagonists such as cimetidine, ranitidine, famotidine etc. are used in the treatment of peptic ulcer and are discussed in chapter Antiulcer agents. ... 

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. 

The modes of action, uses and therapeutic efficacy of these histamine receptor antagonists are essentially those of cimetidine. Differences from cimetidine lie chiefly in dose and profile of unwanted effects. Ranitidine (t / 2 h) is 50%, famotidine (tl 3 h) is 25% and nizatidine (t / 1 h) is 10% metabolised, in each case the remainder being excreted unchanged by the kidney. 

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. 

Famotidine is a histamine H2 receptor antagonist. It does not affect drug metabolism and it has been claimed to be free of the antiandrogenic effect of cimetidine however in one woman who accidentally took double doses of the drug for some months it did cause hyperprolactinemia and breast engorgement (SEDA-18, 372). In other ways it bears a very close resemblance to cimetidine for example, headache and confusion with intravenous use are reported, as are thrombocytopenia and pancytopenia (SEDA-15, 395). 

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