Stomach acidic environment

Seshan K. 1983. How are the physical and chemical properties of chrysotile asbestos altered by a 10-year residence in water and up to 5 days in simulated stomach acid Environ Health Perspect 53 143-148. 

Thus an acidic drug with a relatively low pK of 3 will be largely unionised (hundredfold) in the acidic environment (pH = 1) of the stomach since... 

Helicobacter pylori is a gram-negative microaerophilic rod that has a number of adaptive functions allowing it to live within the acidic environment of the stomach. It is an S-shaped... 

Lanthanum is a naturally occurring trivalent rare earth element (atomic number 57). Lanthanum carbonate quickly dissociates in the acidic environment of the stomach, where the lanthanum ion binds to dietary phosphorus, forming an insoluble compound that is excreted in the feces. Lanthanum has been shown to remove more than 97% of dietary phosphorus... 

Calcium carbonate should be taken with food to maximize absorption. Elderly patients or patients receiving proton pump inhibitors or H2-receptor antagonists may have added difficulty absorbing calcium supplements because of reduced stomach acidity. Better absorption may occur in this setting with calcium citrate because an acid environment is not needed for absorption it may be taken with or without food. 

After the food is swallowed, the digestive process continues in the stomach where the food is attacked by stomach acid. In fact, stomach acid is concentrated hydrochloric acid. The hydrochloric acid, along with an enzyme called pepsin, breaks down proteins in the food. Pepsin can only function in the low pH environment of the stomach. The hydrochloric acid is needed to maintain the low pH that pepsin needs to function. 

Did you know the average American consumes the equivalent of 20 teaspoons of sugar each day The non-nutritive sweetener industry is described as a billion-dollar industry with projections of even more rapid expansion in the next few years. What do chemists look for in their search for an ideal sweetener Consumers seek good-tasting, nontoxic, low-caloric sweeteners. Chemists in the sweetener industry add further demands an inexpensive, easy-to-synthesize product that is readily soluble in water and resists degradation by heat and light is of prime importance. The chemical structure of sucralose keeps the sweetener intact as it passes through the acidic environment of the stomach. Thus, sucralose is not... 

A repetition of in situ experiments with the yellowhead wrasse, partially in response to the above criticisms, again showed that fish developed a learned aversion to otherwise palatable food that had been adulterated with 15P-PGA2 [99], This was presumably due to the emetic properties of PGA2. It was pointed out that methyl esters of prostaglandins are also known to possess emetic properties [104], and reasoned that if the 15-acetoxy ester inhibits the emetic properties of PGA2, then it is likely to be quickly lost because of its known lability, especially in the presence of coral esterase. Further, the acidic environment in the stomachs of predatory fish would promote hydrolysis of these labile esters. 

In the stomach, carotenoids are exposed to acid environments. This can lead to carotenoid isomerization, which can change carotenoid antioxidant properties, solubility, and absorption. In humans, (3-carotene absorption is reduced when the pH of the gastric fluids is below 4.5 (Tang and others 1995). Vitamin E consumption seems to reduce carotenoid absorption in animals, presumably because vitamin E and carotenoids compete for absorption (Furr and Clark 1997). Dietary sterols, such as those in sterol-supplemented functional foods, are also known to decrease carotenoid absorption. 

Nasal Administration. A route that has gained increasing popularity of late for pharmaceutical administration in humans is the intranasal route. The reasons for this popularity are the ease of use (and, therefore, ready patient acceptance and high compliance rate), the high degree and rate of absorption of many substances (reportedly for most substances up to 1000 molecular weight McMartin et al., 1987), and the avoidance of the highly acid environment in the stomach and first-pass metabolism in the liver (particularly important for some of the newer peptide moieties) (Attman and Dittmer, 1971). The only special safety concerns are the potential for irritation of the mucous membrane and the rapid distribution of administered materials to the CNS. 

Enteric coated tablets are designed to resist the acidic environment in the stomach and release the medication in the small intestine. If such tablets are broken, their enteric properties may be lost. Therefore, do not break them. 

Absorption. Absorption of cyanide across the gastrointestinal mucosa depends on the pH of the gut and the pKa and lipid solubility of the particular cyanide compound. Hydrogen cyanide is a weak acid with a pKa of 9.2 at 25 °C. The acidic environment in the stomach favors the non-ionized form of hydrogen cyanide and facilitates absorption. Information regarding the rapid lethal effects following oral intake of cyanide in humans (Gosselin et al. 1976) indicates that cyanide is rapidly absorbed from the gastrointestinal tract. 

In this as in all other problems of experimental design, prior information is helpful. For example, if the enzyme we are dealing with is naturally found in a neutral environment, then it would probably be most active at a neutral pH, somewhere near pH = 7. If it were found in an acidic environment, say in the stomach, it would be expected to exhibit its optimal activity at a low (acidic) pH. When information such as this is available, it is appropriate to center the experimental design about the best guess of where the desired region might be. In the absence of prior information, factor combinations might be centered about the midpoint of the factor domain. 

Enteric coating materials not only protect a dosage form from the acidic environment in the stomach and allow drug delivery to the small intestine, they may also pass through the... 

Workers exposed to an airborne fluoride concentration of 5mg/m complained of eye and respiratory tract irritation and nausea. The lethal oral dose of sodium fluoride for humans has been estimated to be 32-65 mg F/kg of body weight. Effects from ingestion are diffuse abdominal pain, diarrhea, and vomiting excessive salivation, thirst, and perspiration painful spasms of the limbs and sometimes albuminuria." Gastrointestinal effects produced after the acute ingestion of toxic amounts of fluoride likely arise from the corrosive action of hydrofluoric acid, which is produced within the acidic environment of the stomach. Cardiac arrest after accidental exposure to high levels of fluoride has been attributed to the development of hypocalcemia and/or hyperkalemia. ... 

Various factors are required for regular fat digestion. Sublingual lipase and eventually a gastric lipase — which are both stable in an acidic environment — start digesting dietary fats in the stomach. In the intestine, pancreatic bicarbonate as well as bile acids are essential for emulsification of fats and fat-soluble substances which are then cleaved by pancreatic lipases. The cleavage products are incorporated into micelles and can then penetrate the unstirred water layer (UWL) which covers the intestinal surface. There, they can deliver the cleavage products of dietary fats as well as fat-soluble substances (e.g., carotenoids, vitamin E, vitamin A) to the luminal surface of the enterocytes. 

In the acidic environment of the stomach, drugs that are weak acids, such as aspirin, are in their pro-tonated or nonionized form, which can be taken up by the gastric mucosal cells. 

When ionic fluoride enters the acidic environment of the stomach lumen, it is largely converted to weak acid hydrogen fluoride (HF) with a pKg of 3.45 [17], The higher acidity of the stomach speeds up the process of absorption by passive diffusion from both the stomach and the small intestine, suggesting that fluoride is absorbed from the stomach as undissociated hydrogen fluoride rather than as fluoride ion [63,72]. Most of the fluoride that is not absorbed from the stomach will be rapidly absorbed from the small intestine. There is no convincing evidence that active transport processes are involved [17]. 

Aspirin s original use as an analgesic, antipyretic, and to reduce inflammation continues to this day, and more recently some evidence has been found that it may lessen the chance of heart attacks due to its effect as a blood thinner. Just as aspirin continues to provide the same benefits as a century ago, it also produces some of the same problems. The major problem is that it can upset the stomach. In the acidic environment of the stomach, aspirin can diffuse through the protective mucous lining of the stomach and rupture cells and produce bleeding. Under normal doses, the amount of blood loss in most individuals is only a milliliter or two, but in some individuals who take heavy doses bleeding can be severe. To counterattack this side effect, manufacturers include an antacid such as aluminum hydroxide and call the aspirin a buffered aspirin. As noted previ-... 

Indinavir requires an acidic environment for optimum solubility and therefore must be consumed on an empty stomach or with a small, low-fat, low-protein meal for maximal absorption (60-65%). The serum half-life is 1.5-2 hours, protein binding is approximately 60%, and the drug has a high level of cerebrospinal fluid penetration (up to 76% of serum levels). Excretion is primarily fecal. An increase in AUC by 60% and in half-life to 2.8 hours in the setting of hepatic insufficiency necessitates dose reduction. 

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