Colonic time controlled

The relatively constant transit time in the small intestine of approximately 3-4 h is another physiological characteristic which can be exploited to achieve colon specificity (time-controlled drug release). After gastric empt5ung, a time-controlled drug delivery system is intended to release the drug after a predetermined lag phase. 

This time controlled release tablet with a designated lag time followed by a rapid release may provide an alternative to site-specific delivery of drugs with optimal absorption windows or colonic delivery of drugs that are sensitive to low pH or enzyme action for the treatment of localized conditions such as ulcerative colitis, Crohn s disease, and irritable bowel syndrome (IBS). Also, by controlling a predetermined lag time of drug from dosage form, the release behavior can be matched with the body s circadian rhythm pattern in chronotherapy. 

Niwa, K., Takaya, T., Morimoto, T., and Takada, K. (1995), Preparation and evaluation of a time-controlled release capsule made of ethylcellulose for colon delivery of drugs, J. Drug Target., 3, 83-89. 

Insert current time CONTROL+ (colon) CONTROL+ (colon) or... 

Bouchoucha et al. characterized colonic transit time in 30 healthy subjects and in 43 patients with inflammatory bowel disease using X-ray opaque markers. The response to food was different in the two populations in controls, the cecum and ascending colon emptied and filled the distal bowel, whereas in the patients only the splenic flexure and left transverse colon emptied. Movement through both the right and left colon in patients was observed to be much slower than in controls, both before and after a meal [55]. 

Rao et al. [140] described a study using a commercial pH sensitive radio-telemetry capsule (RTC) to evaluate small bowel and colonic transit time in athletes with gastrointestinal symptoms. The RTC (type 7006 Remote Control Systems, London, UK) consists of a glass electrode with an integral reference cap and battery. RF transmissions from the capsule are detected by a solid-state receiver worn on the belt of the patient. The recorder samples the pH from the capsule at 6 second intervals for a period of 24 hours. They used pH changes as an indication of the pH capsule s movement. A sharp rise in pH from around pH 2 to pH 6 indicates that the capsule has moved into the duodenum from the stomach. Then the pH progressively rises to a plateau around pH 8, which indicates that the capsule has moved into the terminal ileum. Another commercially available wireless pH sensor (Bravo) from Medtronic Inc. has been used to measure esophageal pH for a period of 48 hours and it will be discussed later. 

Vandelli, M.A., Leo, E., Fomi, F., and Bemahei, M.T., In vitro evaluation of a potential colonic delivery system that releases drug after a controllable lag-time, Eur. J. Pharm. Bio-pharm.,Ai-. A%- 5 (1996). 

Mycelium fully covered the surfaces of isocyanate-bonded control flakeboards within 1 week, but mycelial development was significantly slower in phenol-formaldehyde-bonded control flakeboards. Both isocyanate- and phenol-formaldehyde-bonded acetylated flakeboards showed surface mycelium colonization during the test time, but the fungus did not attack the acetylated flakes, so little strength was lost. 

Cut, Pile and Burn. While some natural enemies do survive other direct controls, most are killed as a result of this long-used tactic. Much of the mortality to natural enemies incurred from use of the aforementioned tactics could be eliminated by treating only those trees that contain active beetle populations. T. dubius and other predators have a longer developmental time than their host. Since parasites arrive later in the colonization process, they also remain in trees after pest emergence. 

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