Gastrointestinal delivery systems

Hejazi, R., and M. Amiji. 2003. Chitosan-based gastrointestinal delivery systems. J Control Release 89 151. 

Chitosan Beads, Microcapsules and Microspheres for Gastrointestinal Delivery Systems... 

Hejazi, R Amiji, M. Chitosan-based gastrointestinal delivery systems. Jovmal of Controlled Release, 89, 2003,151-165. 

Fiebrig I (1995) Solution Studies on the Mucoadhesive Potential of Various Polymers for use in Gastrointestinal Drug Delivery Systems. PhD Thesis, University of Nottingham, Nottingham, UK... 

In the gastrointestinal tract, a mucoadhesive drug delivery system provides advantages in prolonging the residence time of devices. The use of pH-sensitive bioadhesive polymers has been proposed [26], An extensive review of pH-sensi-tive hydrogels is given by Brpndsted and Kopecek [27],... 

PK Gupta, S-H Leung, JR Robinson. Bioadhesive/mucoadhesives in drug delivery to the gastrointestinal tract. In V Lenaerts, R Gurny, eds. Bioadhesive Drug Delivery Systems. Boca Raton, FL CRC Press, 1990, pp 65-92. 

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. 

This model consists of a total of five compartments, the drug delivery system (DDS), the gastrointestinal tract (GIT), the central compartment (Central), and two elimination compartments denoted with a dashed box outline, one for pre-systemic elimination (Unavailable) and one for... 

Noninvasive drug delivery may require the administration of the drug delivery system (DDS) at an epithelium as a suitable site of absorption of the active compormd. Such regions are usually called mucosae. In the human body several mucosal sites can be identified, the one mostly used for administration and absorption of therapeutics being the gastrointestinal route. In order to increase the residence time at these absorption sites, a so-called mucoadhesive delivery system has to be used. Generally, these systems consist of one or more types of hydrogels. 

Of the indirect inhibitors of thrombin are the he-parins and new delivery systems have been improved with a generation of molecules that can be absorbed by the gastrointestinal tract. 

Hydrophobic polymers are often used to deliver biomacromolecules regardless of the route of administration. The rapid transit time of approximately 8 hours limits the time of a device in the gastrointestinal (GI) system, consequently the mechanisms possible for oral drug release are limited. The predominant method of release from hydrophobic polymers has been degradation, or biodegradation, of a polymeric matrix by hydrolysis (Figure 11.1). In fact, all of the hydrophobic polymers described in this chapter for use as oral protein or peptide delivery are hydrolytically unstable. 

Anticholinergics -gastrointestinal agents [GASTROINTESTINAL AGENTS] (Vol 12) -role in drug delivery [DRUG DELIVERY SYSTEMS] (Vol 8)... 

Kossena, G. A., W. N. Charman, B. J. Boyd, D. E. Dunstan, and C. J. H. Porter. 2004. Probing drug solubilization patterns in the gastrointestinal tract after administration of lipid-based delivery systems A phase diagram approach).. Pharm. Sci93 332-348. 

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