Drug delivery systems luminal

Among newly developed colon-specific drug delivery systems, pressure-controlled delivery capsules (PCDCs) [161] can be mentioned. Their mechanism of action is based on the relatively strong peristaltic waves taking place in the colon and leading to an increased luminal pressure. They consist of a capsular-shaped suppositories coated with a water-insoluble polymer (ethyl cellulose). Once taken orally, PCDCs behave like an ethyl cellulose balloon, because the suppository base liquefies at body temperature. In the upper GI tract, PCDCs are not directly subjected to the luminal pressures since sufficient fluid is present in the stomach and small intestine. The reabsorption of water in the colon provokes an increase of the luminal content viscosity. As a result, increased intestinal pressures directly affect the system via colonic peristalsis. Consequently, PCDCs mpture and drug release in the colon take place. 

Bernkop-Schnurch A, Gockel NC (1997) Development and analysis of a polymer protecting from luminal enzymatic degradation caused by a-chymotrypsin. Drug Dev Ind Pharm 23 733-740 Bernkop-Schnurch A, Kast CE, Guggi D (2003) Permeation enhancing polymers in oral delivery of hydrophilic macromolecules thiomer / GSH systems. J Control Release. 2003 Dec 5 93(2) 95-103. 

ABSORPTION AND ELIMINATION The oral bioavailabilities, plasma tj, and routes of elimination of inhibitors of Na+-K+-2CL symport are listed in Table 28. Because these drugs are bound extensively to plasma proteins, their delivery to the tubules by filtration is limited. However, they are secreted efficiently by the organic acid transport system in the proximal tubule and thereby gain access to their binding sites on the Na+-K+-2Q" symporter in the luminal membrane of the TAL. 

---