Absorption through gastrointestinal system

Casein refers to a family of proteins, namely, ttgi-, 0. 2-, p-, and k-caseins (Table 5.1). Digestion of a- and p-caseins leads to production of peptides that may bind to opioid receptors that exist in the nervous, endocrine, immime, or gastrointestinal system (Kampa et ah, 1996 Meisel, 2004). These compoimds may modulate absorption processes in the gut and can potentially affect gastrointestinal fimction through transit... 

Encapsulation within an enteric coat (resistant to low pH values) protects the product during stomach transit. Microcapsules/spheres utilized have been made from various polymeric substances, including cellulose, polyvinyl alcohol, polymethylacrylates and polystyrene. Delivery systems based upon the use of liposomes and cyclodextrin-protective coats have also been developed. Included in some such systems also are protease inhibitors, such as aprotinin and ovomucoids. Permeation enhancers employed are usually detergent-based substances, which can enhance absorption through the gastrointestinal lining. 

The gastrointestinal system of zebrafish presents clear differences from the human system. The zebrafish does not possess a stomach, the intestine is continuous with the pharynx through a short esophagus, and no sphincters are present [61]. However, zebrafish have most of the cell types observed in the small intestine -absorptive, endocrine, goblet, and interstitial cells of Cajal, although Paneth cells are absent. Gut contractions are under the control of the enteric nervous systems, which respond to different pharmaceuticals in similar way as the mammalian counterpart. For example, zebrafish embryos can be used as predictor of emetic response to pharmaceuticals, one of the most commonly reported clinical adverse effects to be considered in the development of new dmgs [61]. 

The diterpene salvinorin A from Salvia divinorum (Epling and Jativa-M), in doses of 200-500 pg produces effects which are subjectively identical to those experienced when the whole herb is ingested. Salvinorin A is effectively deactivated by the gastrointestinal system, so alternative routes of absorption must be used to maintain its activity. Traditionally the herb is consumed either by chewing the fresh leaves or by drinking the juices of freshly crushed leaves. The effects of the herb when consumed this way depend on absorption of salvinorin A through the oral mucosa before the herb is swallowed. 

It is clear that to exert a toxic effect a compound must come into contact with the biological system under consideration. It may exert a local effect at the site of administration on initial exposure, but it must penetrate the organism in order to have a systemic effect. The most common means of entry for toxic compounds are via the gastrointestinal tract and the lungs, although in certain circumstances, absorption through the skin may be an important route. Therapeutic agents may also enter the body by other routes such as injection. 

Adverse Effects. Nystatin is generally well tolerated when applied locally. Systemic absorption through mucous membranes may cause some gastrointestinal disturbances (nausea, vomiting, diarrhea), but these side effects are generally mild and transient. Topical use of butenafine, naftifine, and tolnaftate is likewise safe, although local burning and irritation of the skin may occur in some individuals. 

The gastrointestinal tract may be regarded as a tube through the body from the mouth to the anus, the contents of which are external to the rest of the organism system. Therefore, any systemic effect of a toxicant requires its absorption through the mucosal cells that line the inside of the gastrointestinal tract. Caustic chemicals can destroy or damage the internal surface of the tract and are viewed as nonkinetic poisons that act mainly at the site of exposure. 

Epling and Jativa-M) containing the neoclerodane diterpene divinorin A or salvinorin A (Fig. 12.1). It was the first documented non-alkaloidal diterpene hallucinogen. It is inactivated by the gastrointestinal system if orally ingested, and the effect is produced after absorption through the oral mucous. 9... 

DNOC is absorbed rapidly by the respiratory and gastrointestinal tracts. Methods to reduce its absorption require that the amount of time prior to treatment be minimized. Although absorption through skin is slower than via inhalation and oral rautes, reducing dermal exposure is important because DNOC is not modified in the skin and systemic effects can occur. 

The most striking effect of systemic absorption of cocaine is central nervous system stimulation. Signs and symptoms can include excitement, restlessness, rapid and irregular pulse, dilated pupils, headache, gastrointestinal upset, delirium, and convulsions. Death usually results from respiratory feilure. Moderate doses of cocaine can also raise body temperature. Systemic absorption through mucous membranes is rapid and has been compared in speed with that of intravenous administration. 

Of the two types of bone marrow toxicity that chloramphenicol can cause, it may cause the late type only in genetically predisposed patients. The overall risk of aplastic anemia after oral administration of chloramphenicol is 1 30 000 to 1 50 000, which is 13 times greater than the risk of idiopathic aplastic anemia in the population as a whole. Since topical administration achieves systemic effects by absorption through the conjunctival membrane or through drainage down the lacrimal duct, with eventual absorption from the gastrointestinal tract, the risk may be similar to that after oral administration. However, based on two case-control studies and a cohort study, the incidence of blood dyscrasias due to chloramphenicol eye-drops was estimated to be somewhat lower, namely 1 100 000 treated patients (40,66). 

The efficacy and safety of tiotropium have been studied in vitro and in early clinical trials, and dose-ranging studies have shown that tiotropium dry powder 18 micro-grams/day is safe and efficacious (1,4,5). Since the quaternary structure of tiotropium limits its absorption through the mucous membrane of the respiratory and gastrointestinal tract, systemic adverse effects are in general minimal. 

Mouthwashes, toothpastes and other preparations are introduced into the oral cavity for local prophylactic and therapeutic reasons. It is not known to what extent components of these formulations are absorbed and give rise to systemic effects. The absorption of drugs through the oral mucosa, however, provides a route for systemic administration which avoids exposure to the gastrointestinal system. Dmgs absorbed in this way bypass the liver and have direct access to the systemic circulation. The sublingual, buccal and gingival... 

The immediate and long-term effects of a pollutant are directly related to the mode of entry. The portals of entry for an atmospheric pollutant are the skin, gastrointestinal tract, and lungs. For a toxicant, by far the most common means of entry into the body system is by absorption through the skin. In this case, the points of entry are through the hair follicles, sweat glands, and open wounds. 

Reeves 1991a). The intact skin presents a relatively good barrier to beryllium, and insoluble compounds of beryllium have been shown to penetrate the skin only after trauma. Soluble beryllium compounds can cause local irritation, but systemic absorption is thought to be minimal. Similarly, absorption through the gastrointestinal tract is minimal and a U.S. Public Health Service study (Hyslop etal. 1943) established that only 0.006% of ingested beryllium was absorbed. The absorption of beryllium occurs mainly in the acid environment of the stomach. Once the beryllium passes into the alkaline intestine, it becomes precipitated as a phosphate and is excreted in the feces (Vorwald and Reeves 1959). 

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