Gastric antacids

Sodium bicarbonate is a gastric antacid that may cause systemic alkalosis on overdose and may contribute to edema owing to sodium retention. It is useful for systemic acidosis because both deficient ions are present in the same molecule, and it can be used topically as a moist paste or in solution as an antipmritic. Sodium bicarbonate also is an ingredient of many effervescent mixtures, alkaline solutions, etc. One gram of NaHCO neutralizes 115 mL 0.1 NHCl. 

Potassium bicarbonate is used in baking powder and effervescent salts. In medicine, the salt is a gastric antacid and an electrolyte replenisher. It also is dry powder in fire extinguishers. 

Herzog P, HoltermUller KH, Kasper W, Meinertz T, Trenk D, Jahnchen E. Absorpticn of mexiletine after treatment with gastric antacids. BrJ Clin Pharmacol ( 9S2) 14,746-7. 

Magnesium oxide is an effective nonsystemic antacid, ie, it is converted to the hydroxide. It does not neutralize gastric acid excessively nor does it hberate carbon dioxide. The light form is preferable to the heavy for adininistration in Hquids because it is suspended more readily. One gram of magnesium oxide neutralizes 87 mL of 0.1 NUCl in 10 min, and 305 mL in 2 h. 

Ketoconazole. For treatment of systemic mycoses with amphotericin B or miconazole, the patient must be admitted to a hospital. This is not always possible, particularly in areas where systemic mycoses occur frequently, nor is it always desirable, because of the expense. For these reasons, it was desirable to find an antimycotic that combined safety and broad-spectmm activity with oral adraiinistration. Ketoconazole (10), which is orally active, met most of these requirements. This inhibitor of the ergosterol biosynthesis is an A/-substituted imidazole, that differs from its precursors by the presence of a dioxolane ring (6,7). Ketoconazole is rapidly absorbed in the digestive system after oral adrninistration. Sufficient gastric acid is required to dissolve the compound and for absorption. Therefore, medication that affects gastric acidity (for example, cimetidine and antacids) should not be combined with ketoconazole. 

Chemical changes in the cellular environment include inactivation of cellular functions or the alteration of the chemical components of body fluid, such as a change in the pH. For example, antacids neutralize gastric acidity in patients with peptic ulcers. 

Dofetilide is not administered with cimetidine because dofetilide plasma levels may be increased by as much as 50%. When treatment for gastric disorders is necessary, patients receiving dofetilide should take omeprazole ranitidine, or antacids as an alternative to cimetidine. 

This electrolyte plays a vital role in the acid-base balance of the body. Bicarbonate may be given IV as sodium bicarbonate (NaHC03) in the treatment of metabolic acidosis, a state of imbalance that may be seen in diseases or situations such as severe shock, diabetic acidosis, severe diarrhea, extracorporeal circulation of blood, severe renal disease, and cardiac arrest. Oral sodium bicarbonate is used as a gastric and urinary alkalinizer. It may be used as a single drug or may be found as one of the ingredients in some antacid preparations. It is also useful in treating severe diarrhea accompanied by bicarbonate loss. 

Levodopa, a dopamine precursor, is the most effective agent for PD. Patients experience a 40% to 50% improvement in motor function. It is absorbed in the small intestine and peaks in the plasma in 30 to 120 minutes. A stomach with excess acid, food, or anticholinergic medications will delay gastric emptying time and decrease the amount of levodopa absorbed. Antacids decrease stomach acidity and improve levodopa absorption. Levodopa requires active transport by a large, neutral amino acid transporter protein from the small intestine into the plasma and from the plasma across the blood-brain barrier into the brain (Fig. 29-2). Levodopa competes with other amino acids, such as those contained in food, for this transport mechanism. Thus, in advanced disease, adjusting the timing of protein-rich meals in relationship to levodopa doses may be helpful. Levodopa also binds to iron supplements and administration of these should be spaced by at least 2 hours from the levodopa dose.1,8,16,25... 

Disruption of host defenses owing to intravenous catheters, indwelling Foley catheters, burns, trauma, surgery, and increased gastric pH (secondary to antacids, H2 blockers, and proton pump inhibitors) may place patients at higher risk for infection. Breaks in and entry into the skin provide a route for infection because the natural barrier of the skin is disrupted. Increased gastric pH can allow for bacterial overgrowth and has been associated with an increased risk of pneumonia.18... 

People of blood type O are more susceptible to El Tor vibrios than people of other blood types.18 Inoculum size affects the likelihood and severity of cholera infection. The infectious dose is lower in patients who are taking antacids owing to the neutralization of gastric acid.19... 

Due to blockage of the main zeolite channels by anions present in the structure, few applications have been reported for these tectosilicates. However, the presence of carbonate anions could make them suitable as antacids. Our group has worked with a series of natural minerals as antacids, such as clays [4], modified carbons [5] and zeolites[6]. In this way, a carbonated cancrinite and its intermediate phase were tested as an antacid with a synthetic gastric juice. 

IR spectra did not show differences between the intermediate phase and the disordered cancrinite. Therefore, IR techniques fail when were used to identify these phases. One more effective way to identify disordered cancrinite and the intermediate phase is by using X-ray diffraction (XRD). Fig 1 shows the diffractogram of both tectosilicates. In the intermediate phase, the observed peaks correspond with those reported in the literature[4]. The main differences between both spectra correspond to those peaks placed between 25°<20<35°, which are more intense for the disordered cancrinite [9]. Likewise, the results of specific surface area for the intermediate phase (sample 5) and the disordered cancrinite (sample 6) were 35 and 41 m2/g respectively. The antacid capacity test was carried out with the samples 5 and 6. Fig. 2 shows the relationship between experimental pH versus the mass content of the tectosilicates. The neutralization capacity of these solids is related with its carbonate content which reacts with the synthetic gastric juice to neutralize it. In general, the behaviour of solids is similar the pH increases as the weight of the studied solid is increased. However, a less disordered cancrinite mass amount must be employed to reach a pH= 4 in comparison... 

Snepar R, Poporad GA, Romano JM, Kobasa WD, Kaye D Effect of cimetidine and antacid on gastric microbial flora. Infect Immun 1982 36 518-524. 

Single or combination nonprescription antacid products, especially those containing magnesium hydroxide, aluminum hydroxide, and/or calcium carbonate, may provide sufficient relief from simple nausea or vomiting, primarily through gastric acid neutralization. 

Factors that theoretically affect bioavailability include alterations in GI transit time, gastric pH, edema of the GI tract, vomiting and diarrhea, and concomitant drug therapy, especially antacid or H2-antagonist administration. 

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