Gastrointestinal tract resorption

The hemolytic anemia caused in pregnant rabbits by diflunisal was severe enough to explain the concomitant axial skeletal malformations (Clark et ah, 1984). Acetazolamide-induced fetal malformations in mice are apparently related to maternal hypercapnia (Weaver and Scott, 1984a, b) and hypokalemia (Ellison and Maren, 1972). The increased resorption rate induced in rabbits by the antibiotic norfloxacin depends on exposure of the maternal gastrointestinal tract (Clark et ah,... 

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. 

Dicloxacillin is absorbed well from the gastrointestinal tract but the presence of food in the stomach reduces resorption. Although cloxacillin differs chemically from oxacillin only in the presence of a chlorine atom, their absorption profile after oral administration is not similar. Cloxacillin is more rapidly and effectively absorbed than oxacillin. However, absorption of all isoxazolyl penicillins is better when given by intramuscular injection. These agents can be also administered by intravenous, intrauterine, intra-articular, intrapleural, and intramammary injections. 

In 1960, Volkheimer [31] elegantly demonstrated resorption of starch from the human gastrointestinal tract and its appearance in blood and urine as early as 30-60 min after ingestion reaching peak concentrations after approximately 2 h. 

Normally, drugs reach their target organ via the blood. Therefore, the drug molecules first have to enter the circulation, which requires the passage through barrier membranes in the gastrointestinal tract. This process is called resorption or absorption. 

The pharmacokinetics of XYZ1234 formulations after release in different regions of the gastrointestinal tract reveal similar exposure for the proximal small bowel as compared to the immediate release formulation, halved exposure for the distal small bowel and only poor absorption from the ascending colon. Thus colonic resorption cannot be relied on for the development of an extended release formulation. Analysis of the scintigraphic data has confirmed release of the formulation at the target locations in the required number of subjects. 

In ecosystems, Pu is present mainly in the form of sparingly soluble Pu(IV) dioxide or hydroxide and is therefore rather immobile. It stays mainly in the upper layers of the soil and its uptake by roots is very small (soil-plant transfer coefficients <0.001 d/kg). However, plants may be contaminated with Pu by deposition from the air. Resorption factors in the gastrointestinal tract of animals are also very small (/r < 10 " ). On the other hand, up to 5% of inhaled Pu is found in blood and up to 15% in the lymph glands. About 80% of resorbed Pu is deposited in bones, the rest in kidneys and liver. Biological half-lives reported in the literature vary between 500 and 1000 d for the lymph glands and between 1 and lOO y for the skeleton. 

Due to the poor resorption of liquid mercury from the gastrointestinal tract, an ingestion of liquid metallic mercury is acutely less toxic. The swallowing of 100-200 g of liquid mercury by an adult resulted in no signs of a systemic intoxication (Sataw etal. 2001, Schafer etal. 1994). Normally, a mercury thermometer, when broken in the anus of an infant, would not result in any signs of intoxication. Inhalation of mercury vapor spilled from a thermometer is much more critical, however, especially in tiny rooms such as an incubator (McLaughlin... 

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