Acid , gastric

Gas solubility Gas sweetening Gas-treating Gastric acid Gastric prokinetics Gastrin... 

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. 

H2 The H2 receptor mediates effects, through an increase in cycHc adenosine monophosphate (cAMP), such as gastric acid... 

From a therapeutic point of view, selective agonists may become useful in the treatment of heart failure and catecholamine-insensitive cardiomyopathy, but only if compounds become available that do not stimulate gastric acid secretion or cause other unforeseen problems. 

Histamine H2 Receptor Antagonists. In 1972 a new class of histamine antagonists was described that was capable of antagonizing histamine-induced gastric acid secretion (6). The H2 antagonists are divided into five stmctural classes, some of which are shown in Table 3. A more complete review can be found in Reference 25. 

For control of gastric acid secretion, the H2 antagonists have encountered competition from the potent -ATPase inhibitors such as... 

Moreover, receptors also control gastric acid release, although some marked species dependence is noticed (8). However, appHcation of agonists in this area does not seem to be probable the antagonists and the proton pump inhibitors serve quite weU. 

Biologica.1 Activities a.ndAna.logues, The many pharmacological actions of neurotensin include hypotension, increased vascular permeabihty, hyperglycemia, increased intestinal motility, and inhibition of gastric acid secretion (120). In the brain, it produces analgesia at remarkably low doses (121). 

CCK is found in the digestive tract and the central and peripheral nervous systems. In the brain, CCK coexists with DA. In the peripheral nervous system, the two principal physiological actions of CCK are stimulation of gaU. bladder contraction and pancreatic enzyme secretion. CCK also stimulates glucose and amino acid transport, protein and DNA synthesis, and pancreatic hormone secretion. In the CNS, CCK induces hypothermia, analgesia, hyperglycemia, stimulation of pituitary hormone release, and a decrease in exploratory behavior. The CCK family of neuropeptides has been impHcated in anxiety and panic disorders, psychoses, satiety, and gastric acid and pancreatic enzyme secretions. 

Activation of histamine receptors with histamine and selective agonists such as dimaprit (205) and impromidine (206) results ia gastric acid... 

The pharmacology of penicillins differs markedly from compound to compound but has been well reviewed (57). The majority of derivatives, including penicillin G and the antipseudomonal penicillins, ate unstable in gastric acid and ate not available orally. The isoxazolyl penicillins ate relatively acid stable but not consistendy well absorbed by the oral route. Nafcillin and oxacillin ate poody absorbed orally cloxacillin, dicloxacillin, and ducloxacillin ate more teUable. Penicillin V, ampicillin, and patticulady amoxicillin ate relatively well absorbed orally. Esters of ampicillin such as bacampicillin, pivampicillin, and talampicillin improve the level of oral absorption of ampicillin to that achieved by amoxicillin. Absorption can be diminished by food after oral adruinistration, however, and peak blood levels, usually achieved after 1 to 2 h, ate somewhat delayed after ingestion of food. 

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. 

Bis(pyridiniumthio)quaternary compounds gastric acid secretion and, 2, 519 Bis(selenadiazoles) decomposition, 6, 349... 

Histamine is a biogenic amine that is widely distributed in the body and functions as a major mediator of inflammation and allergic reactions, as a physiological regulator of gastric acid secretion in the stomach, as a neurotransmitter in the central nervous system (CNS) and may also have a role in tissue growth and repair. 

The histamine H2-receptor (359 amino acids) is best known for its effect on gastric acid secretion. Histamine H2-receptor activation, in conjunction with gastrin and acetylcholine from the vagus, potently stimulate acid secretion from parietal cells. High concentrations of histamine are also present in cardiac tissues and can stimulate positive chronotropic and inotropic effects via H2-receptor stimulation and activation of adenylyl... 

Fellenius E, Berglindh T, Sachs Getal(1981) Substituted benzimidazoles inhibit gastric acid secretion by blocking (H+ + K+)ATPase. Nature 290 159-161... 

Gastrointestinal tract Inhibition of most gut hormones, gastric acid, pepsin, bile and colonic fluid secretion... 

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. 

Decreased gastric acidity decreased gastric motility... 

Heparin inhibits the formation of fibrin clots, inhibits the conversion of fibrinogen to fibrin, and inactivates several of the factors necessary for the clotting of blood. Heparin cannot be taken orally because it is inactivated by gastric acid in the stomach therefore, it must be given by injection. Heparin has no effect on clots that have already formed and aids only in preventing the formation of new blood clots (thrombi). The LMWHs act to inhibit clotting reactions by binding to antithrombin HI, which inhibits the synthesis of factor Xa and the formation of thrombin. 

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). 

The proton pump inhibitors suppress gastric acid secretion by blocking the final step in the production of gastric acid by the gastric mucosa... 

Figure 3.1 A schematic representation of the control mechanism that stimulates gastric acid secretion, and the intervention points used to treat ulcers. The parietal cells and gastric cells form part of the epithelial cell lining of the stomach. Histamine release is usually triggered as part ofthe enteric nervous system response to distension of the stomach when food is eaten.

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