Gastrointestinal segments

Folwaczny, C., et al., Measurement of transit disorders in different gastrointestinal segments of patients with diabetes mellitus in relation to duration and severity of the disease by use of the metal-detector test, Zeitschr. Gastroenterol. 1995, 33, 517-526. 

Tran HTT, Tran PHL, Lee B-J (2009) New findings on melatonin absorption and alterations by pharmaceutical excipients using the Ussing chamber technique with mounted rat gastrointestinal segments. Int J Pharm 378(l-2) 9-16... 

When it comes to the pH range of different gastrointestinal segments (pH 1-8), early studies concerning the use of cationic polymers in drug delivery focused on providing environmentally responsive dmg release for oral... 

Distinguish between the two types of gastrointestinal motility segmentation and peristalsis... 

Niclosamide inhibits oxidative phosphorylation and stimulates adenosine tripho-sphatese activity in the mitochondria of cestodes, killing the scolex and proximal segments of the tapeworm both in vitro and in vivo. The scolex of the tapeworm, then loosened from the gut wall, may be digested in the intestine and thus may not be identified in the stool even after extensive purging [90,91], Niclosamide is not appreciably absorbed from the gastrointestinal tract [92,93] and the side effects have primarily been limited to gastrointestinal symptoms. 

The mechanism of iron and heme uptake by the intestine is becoming better understood 70-72), but clearly heme-iron is more efficiently absorbed from the gastrointestinal tract than inorganic iron 73-75), and there is a receptor for heme in the duodenal brush border membrane 76). Duodenal mucosal cells efficiently catabolize heme, and iron-transferrin can be detected in the plasma of blood vessels draining the intestinal segment shortly after Fe—heme—histidine is administered (75). 

Another important advance adding to the value of PBPK modeling in the pharmaceutical industry are physiological, mechanistic models developed to describe oral absorption in humans and preclinical species. Oral absorption is a complex process determined by the interplay of physiological and biochemical processes, physicochemical properties of the compound and formulation factors. Physiologically based models to predict oral absorption in animals and humans have recently been reviewed [18, 19] and several models are now commercially available. The commercial models have not been published in detail because of proprietary reasons but in essence they are transit models segmenting the gastrointestinal tract... 

Niclosamide is a salicylamide derivative. Its mechanism of action could be based on inhibition of oxidative phosphorylation or on its ATPase stimulating action. The scolices and segments, but not segments of the ova, are rapidly killed. Niclosamide is minimally absorbed from the gastrointestinal tract and excreted, mostly unchanged, in the faeces. It is generally well tolerated with occasional gastrointestinal disturbances. Skin eruptions have been reported. 

Drugs that contain 5-aminosalicylic acid (5-ASA) have been used successfully for decades in the treatment of inflammatory bowel diseases (Figure 62-8). 5-ASA differs from salicylic acid only by the addition of an amino group at the 5 (meta) position. Aminosalicylates are believed to work topically (not systemically) in areas of diseased gastrointestinal mucosa. Up to 80% of unformulated, aqueous 5-ASA is absorbed from the small intestine and does not reach the distal small bowel or colon in appreciable quantities. To overcome the rapid absorption of 5-ASA from the proximal small intestine, a number of formulations have been designed to deliver 5-ASA to various distal segments of the small bowel or the colon. These include sulfasalazine, olsalazine, balsalazide, and various forms of mesalamine. 

Miosis is a characteristic symptom of opiate administration, and while tolerance develops to many of the pharmacological effects of this class of drugs, tolerance to the miotic effects occurs at a much slower rate. Miosis is due to an excitatory action of the autonomic segment of the nucleus of the oculomotor nerve, an effect attributed to the stimulation of the mu receptors. In general, it would appear that the actions of morphine and its analogues on the brain, spinal cord and gastrointestinal tract are due to stimulation of the mu receptors. 

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