Individuals with incidence of heartburn or dyspepsia less than three times per week may find antacids sufficient in their ability to provide rapid, short-term (1 to 2 hour) acid neutralization. (Antacids work faster than H2 antagonists but do not last as long). Mucosal protective agents Misoprostol (Cytotec), sucralfate, bismuth subsalicylate* (Pepto Bismol). Gastrointestinal mucosa produces a number of prostaglandins. Mucosal prostaglandins stimulate mucus and bicarbonate secretion and mucosal blood flow. These structures act similarly to hormones in that they stimulate target cells into action, but differ from hormones in the fact that they act locally, near where they are produced. Misoprostal is a prostaglandin analog able to inhibit acid and protect mucosal areas by stimulating mucus and bicarbonate secretion and increasing mucosal blood flow. Sucralfate is a salt that forms a viscous material that binds specifically to ulcers or areas of wear for a period up to 6 hours. It forms a physical barrier that prevents additional abrasion of the area as well as stimulating mucosal prostaglandin and bicarbonate secretion. Little sucralfate is absorbed by the body, and so has few side effects. Usage leaves a residue of aluminum salt, causing constipation in 2 percent of the population, so should not be used for any length of time in patients with renal problems. Mucosal protective agents may interact with other medications, reducing their absorption by the body. Sucralfate is shown to be effecting in healing duodenal ulcers, but may be less effective than proton pump inhibitors. In some cases, individuals taking NSAIDS who experience dyspepsia are prescribed sucralfate. Because peptic ulcers develop in up to 20 percent of individuals who take NSAIDs over the long-term, mucosal protective agents have been used to inhibit the incidence of NSAID-induced ulcers and ulcer-related complications significantly. However, the need for multiple doses daily and the high rate of side effects limits its use, although they may be the most appropriate course of action for individuals at high risk of NSAID complications. Ten to 20 percent of patients may experience abdominal cramping and diarrhea. Colloidal bismuth compounds like bismuth subsalicylate (Pepto Bismol) is the only bismuth compound available in the U.S. Less than 1 percent of bismuth is absorbed, with more than 99 percent of the drug eliminated in the stool. Salicylate is easily absorbed and eliminated in the urine. Bismuth coats ulcers and erosions in the same way as sucralfate, producing a protective layer against gastric juices. Bimuth may also stimulate prostaglandin, bicorbonate and mucus secretion. Bismuth subsalicylate tends to reduce bowel movement frequency and liquidity in the case of some diarrhea. Bismuth is sometimes taken before and during trips to counter potential microbial activity or increase in H pylori. Bismuth compounds tend to blacken the stool, but have few other side effects. Liquid formulas may also darken the tongue. Bismuth compounds should only be used for short periods of time and should not be used at all in individuals with poor renal function. Excessive or prolonged use of some bismuth compounds, but not bismuth subsalicylate, may result in symptoms of bismuth toxicity including headaches, confusion, unsteadiness, or seizures. H2 histamine receptor blockers [H2-receptor antagonists] Cimetidin (Tagamet*), famotidine (Pepcid,*) nizatidine, ranitidine (Zantac). H2-receptor blockers (also referred to as H2-receptor antagonists ) were once widely prescribed for acid-peptid diseases. However, since the recognition that the bacteria H pylori plays a role in ulcer disease, more and more acid-peptic conditions are being treated with proton pump inhibitors and antibacterial therapies (see below).
H2 receptor antagonists are currently primarily prescribed for the following conditions: gastroesophageal reflux disease (GERD), nonulcer dyspepsia, and for the prevention of bleeding from stress-related gastritis. Clients with heartburn or dyspepsia less than three times per week may prefer H2 antagonists to antacids. While they do not work as rapidly, H2 antagonists last for a longer period than antacids (6-10 hours vs. 1-2). Four main H2 antagonists are in current use: cimetidine, ranitidine, famotidine, and niatidine. Each is rapidly absorbed by the intestine. Nizatidine has little first-pass metabolism, with a bioavailability near 100 percent. Cimetidine, ranitidine, and famotidine undergo metabolism by the liver, with a bioavailability of 50 percent. Half-lives for these H2 antagonists range from about 1 to 4 hours, depending on dosage. Elimination is largely a product of hepatic metabolism and renal function. Those with poor renal and hepatic function may need an adjusted dose, with elderly individuals subject to a decline of up to 50 percent in drug clearance and limited volume of distribution. H2 antagonists reduce basal, meal-stimulated, and histamine- stimulated acid secretion, as well as gastrin, in a linear (dose- dependent) fashion. H2 antagonists work by binding to the H2 receptor, which blocks the binding by gastrin and acetylcholine that releases histamine from ECL cells, reducing acid secretion in the process. Each of the four H2 antagonists do this in a different fashion, with H2 antagonists generally more useful in inhibiting the production of acid at night (largely a function of histamine), and less of an impact on meal-stimulated acid. H2 antagonists may be taken before meals to reduce meal- secreted acid, but are more effective for frequent heartburn if taken 2 times per day, which usually reduces symptoms in one- half to three-fourths of subjects studied. Individuals suffering from erosive esophagitis (about one-half of those with GERD) may find some relief with H2-antagonists, but are typically directed to proton-pump inhibitors for treatment. In seriously ill individuals, H2 antagonists are used to reduce the occurrence of bleeding as a result of stress-related gastritis. Less than 3 percent of individuals taking H2 antagonists experience side effects. Those who do may experience headaches, fatigue, constipation or diarrhea, and muscle pain. In cimetidine, specifically, long-term use or high dosages may cause lactation in women and impotence or the development of breasts in men. Cimetidine also alters drug metabolism, resulting in longer half-lives of other medications. As H2 antagonists are able to cross barriers like the placenta and are secreted in breast milk, pregnant and nursing women should not take this drug. Proton pump inhibitors (PPIs) Omeprazole (Prilosec) ezomeprazole (Nexium), lansoprazole (Prevacid), pantroprazole (Protonix), rabeprazole (Aciphex). PPIs have been in use since the late 1980s. They are highly effective acid-inhibiting agents used commonly for treatment of acid-peptic disorders. The five proton pump inhibitors listed above are similar in structure but each works according to a different mechanism. All proton pump inhibitors, except pantophrazole, are administered as oral doses, coated in an acid-resistant coating so it will not be destroyed by stomach- acids. Pantophrazole is administered intravenously. Once the drug is able to pass through the stomach intact, it is largely absorbed in the intestines. Due to lower bioavailability of the drug when taken with food (decreases by 50 percent), administration must be timed carefully around meals, and are most effective when taken on an empty stomach. Proton pump inhibitors block acid secretion at the proton pump pathway. They are effective inhibitors of both meal-stimulated and fasting acid secretion, inhibiting up to 98 percent of acid secretion in a 24-hour period. Proton pump inhibitors have a relatively short half-life (1 ½ hours), but continue to have acid-inhibiting effects for up to 24 hours. In some cases, it
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Book Code: MGA1224
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