Gastrointestinal absorption enhancement

Qi R, Pingel M. Gastrointestinal absorption enhancement of insulin by administration of enteric microspheres and SNAC to rats. J Microencapsul 2004 21(l) 37-45. 

Amino acids promote the production of proteins, enhance tissue repair and wound healing, and reduce the rate of protein breakdown. Amino acids are used in certain disease states, such as severe kidney and liver disease, as well as in TPN solutions. (See the last section of this chapter for a more detailed discussion of TPN.) TPN may be used in patients with conditions such as impairment of gastrointestinal absorption of protein, in patients with an increased requirement for protein, as seen in those with extensive bums or infections, and in patients with no available oral route for nutritional intake ... 

Muranishi, S., Yamamoto, A., Mechanisms of absorption enhancement through gastrointestinal epithelium, in Drug Absorption Enhancement, de Boer, A. G. (ed.), Harwood Academic Publishers, 1994, 67-100. 

Human exposure to endrin may occur by ingestion, inhalation, or by dermal contact. Dermal absorption can be significant. Gastrointestinal absorption is enhanced by dietary fats. While not highly volatile, endrin-laden aerosols or dust particles can be trapped in respiratory mucus and swallowed, leading to gastrointestinal absorption. 

Hu, Z., et al. 2001. A novel emulsifier, Labrasol, enhances gastrointestinal absorption of gentamicin. Life Sci 69 2899. 

Since its discovery, isolation, and purification in the early twentieth century, insulin has been administered to diabetic patients exclusively by injection until the recent introduction of inhaled insulin. Insulin possesses certain physiochemical properties that contribute to its limited absorption from the gastrointestinal tract, and requires subcutaneous injection to achieve clinically relevant bioavailability. With a molecular size of 5.7 kDa, insulin is a moderately sized polypeptide composed of two distinct peptide chains designated the A chain (21 amino acid residues) and the B chain (30 amino acid residues) and joined by two disulfide bonds. Like all polypeptides, insulin is a charged molecule that cannot easily penetrate the phospholipid membrane of the epithelial cells that line the nasal cavity. Furthermore, insulin monomers self-associate into hexameric units with a molecular mass greater than 30 kDa, which can further limit its passive absorption. Despite these constraints, successful delivery of insulin via the nasal route has been reported in humans and animals when an absorption enhancer was added to the formulation. 

Chapter 6 Enhanced Gastrointestinal Absorption of Lipophilic Drugs.Ill... 

Drugs may affect the absorption, distribution, metabolism, or excretion of other drugs. This includes those interactions in which the gastrointestinal absorption of a drug, plasma protein binding, drug metabolism, and urinary excretion are either enhanced or inhibited. 

---