Gastrointestinal tract sodium

Toxicity. Fluoroborates are excreted mostly in the urine (22). Sodium fluoroborate is absorbed almost completely into the human bloodstream and over a 14-d experiment all of the NaBF ingested was found in the urine. Although the fluoride ion is covalently bound to boron, the rate of absorption of the physiologically inert BF from the gastrointestinal tract of rats exceeds that of the physiologically active simple fluorides (23). 

Liquid bromine produces a mild cooling sensation on first contact with the skin. This is followed by a sensation of heat. If bromine is not removed immediately by flooding with water, the skin becomes red and finally brown, resulting in a deep bum that heals slowly. Contact with concentrated vapor can also cause bums and bflsters. Eor very small areas of contact in the laboratory, a 10% solution of sodium thiosulfate in water can neutralize bromine and such a solution should be available when working with bromine. Bromine is especially hazardous to the tissues of the eyes where severely painfiil and destmctive bums may result from contact with either Hquid or concentrated vapor. Ingestion causes severe bums to the gastrointestinal tract (62,63). 

The primary routes of entry for animal exposure to chromium compounds are inhalation, ingestion, and, for hexavalent compounds, skin penetration. This last route is more important in industrial exposures. Most hexavalent chromium compounds are readily absorbed, are more soluble than trivalent chromium in the pH range 5 to 7, and react with cell membranes. Although hexavalent compounds are more toxic than those of Cr(III), an overexposure to compounds of either oxidation state may lead to inflammation and irritation of the eyes, skin, and the mucous membranes associated with the respiratory and gastrointestinal tracts. Skin ulcers and perforations of nasal septa have been observed in some industrial workers after prolonged exposure to certain hexavalent chromium compounds (108—110), ie, to chromic acid mist or sodium and potassium dichromate. 

Interestingly, they report that E. coli, a normal inhabitant of the mammalian gastrointestinal tract, produces anhydro-TTX. Unidentified sodium channel blockers have also been detected in cultures of Vibrio cholerae an estuarine bacterium and human enteropathogen (54). 

The antibiotic is administered orally as the palmitate, which is tasteless this is hydrolysed to chloramphenicol in the gastrointestinal tract. The highly water-soluble chloramphenicol sodium succinate is used in the parenteral formulation, and thus acts as a pro-drug. 

It is conceivable that nltrosamlnes can be synthesized In the Intestine, since the precursors are present. While the conditions for aqueous nltrosatlon reactions are not optimum at pH values encountered In the lower gastrointestinal tract, several studies have shown that these reactions can be catalyzed (39, 40, 41). It has been suggested that the Intestine might be a site for the formation of nltrosamlnes by bacterial action (42). Sander (43) has demonstrated the formation of nltrosamlnes by bacterial action from precursor amines and nitrate at neutral pH and Klubes and coworkers have reported the formation of NDMA. upon Incubation of l C-dlmethylamlne and sodium nitrite with rat fecal contents (44, 45). 

Inorganic compounds such as aluminium hydroxide, sodium bicarbonate, and magnesium and calcium carbonates are commonly used as antacids. There is much scope for the redesign of these agents to achieve fine control of local pH values in the gastrointestinal tract via control of the rate of release of the active bases (e.g., from insoluble compounds). 

All the above mentioned polymers have been evaluated mainly for application in the intestine. Finally, the last part of the gastrointestinal tract, the rectum should also be mentioned as a suitable site for delivery and fast absorption of therapeutics. Kim et al. [88] developed an in situ gelling and mucoadhesive acetaminophen liquid suppository prepared with poloxamers and sodium alginate. It was found that this particular formulation of acetaminophen in humans resulted in shorter T ax and higher maximum plasma concentrations of dmg (C ax) than the conventional acetaminophen suppositories. 

Some of these triiodinated compounds are orally active, i.e. they are absorbed from the gastrointestinal tract after oral administration and imaging of the biliary system is possible following this route of administration. Examples are iopanoic acid, iophenoxic acid and sodium ipodate. A prerequisite for oral absorption is a balance of relatively hydrophilic and lipophilic moieties in the molecule. Numerous investigations have been performed to establish structure-activity relationships for this class of compounds, e.g. by Archer and Hoppe [70, 71]. Sodium salts are better absorbed than the free acids [72]. 

The resorption process is facilitated by the large inner surface of the intestine, with its brush-border cells. Lipophilic molecules penetrate the plasma membrane of the mucosal cells by simple diffusion, whereas polar molecules require transporters (facilitated diffusion see p. 218). In many cases, carrier-mediated cotransport with Na"" ions can be observed. In this case, the difference in the concentration of the sodium ions (high in the intestinal lumen and low in the mucosal cells) drives the import of nutrients against a concentration gradient (secondary active transport see p. 220). Failure of carrier systems in the gastrointestinal tract can result in diseases. 

Although it is marketed as both valproic acid (Depakene) and as sodium valproate (Depakote), it is the valproate ion that is absorbed from the gastrointestinal tract and is the active form. 

Levothyroxine sodium (Levothwid, Synthroid, Levoxine) is the sodium salt of the naturally occurring levorota-tory isomer of T4. It is the preparation of choice for maintenance of plasma T4 and T3 concentrations for thyroid hormone replacement therapy in hypothyroid patients. It is absorbed intact from the gastrointestinal tract, and its long half-life allows for convenient once-daily administration. Since much of the T4 is deiodi-nated to T3, it is usually unnecessary to use more expensive preparations containing bothX4 and Tj.The aim is to establish euthyroidism with measured serum concentrations of T4, T3, and TSH within the normal range. 

Methenamine mandelate is a salt of mandelic acid and methenamine and both of these possess property of urinary antiseptic. It is rapidly absorbed in gastrointestinal tract and excreted unchanged in urine, where it broken down in acidic pH (< 5) of urine and formaldehyde is released, which inhibits most of the bacteria. It is administered with sodium biphosphate, mandelic acid or ascorbic acid to keep the urinary pH below 6. Its use is restricted to chronic, resistant type of UTI. 

Most food absorption takes place in the small intestine. The gastrointestinal tract possesses specialized carrier systems for certain nutrients such as carbohydrates, amino acids, calcium, and sodium. Some xenobiotics use these routes of passage through the cells, while others enter through passive diffusion. 

Absorption of phenytoin is highly dependent on the formulation of the dosage form. Particle size and pharmaceutical additives affect both the rate and the extent of absorption. Absorption of phenytoin sodium from the gastrointestinal tract is nearly complete in most patients, although the time to peak may range from 3 to 12 hours. Absorption after intramuscular injection is unpredictable, and some drug precipitation in the muscle occurs this route of administration is not recommended for phenytoin. In contrast, fosphenytoin, a more soluble phosphate prodrug of phenytoin, is well absorbed after intramuscular administration. 

Sodium sulbactam is poorly absorbed from the gastrointestinal tract and is administered parenterally in combination with ampicillin or cefoperazone. Its pharmacokinetics are similar to those of ampicillin. 

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