Drug absorption interactions

LF Prescott, WS Nimmo, RC Heading. Drug absorption interactions. In DG Grahame-Smith, ed. Drug Interactions. Baltimore Macmillan, 1977, p. 45. 

Many of the interactions covered in this section concern absorption interactions, such as the ability of the tetracyclines and quinolones to chelate with divalent cations. More information on the mechanism of these interactions can be found in Drug absorption interactions , (p.3). 

The various gastrointestinal drug groups covered in this section are listed in Table 27.1 , (see below). Drug absorption interactions , (p.3) discusses how absorption interactions occur and contains more detailed information on some of the mechanisms of interaction covered in this section. 

Another important type of physical chemical interaction that may alter absorption is that of drug binding or adsorption onto the surface of another material. As with complexation and micellarization, adsorption will reduce the effective concentration gradient between gut fluids and the bloodstream, which is the driving force for passive absorption. While adsorption frequently reduces the rate of absorption, the interaction is often readily reversible and will not affect the extent of absorption. A major exception is adsorption onto charcoal, which in many cases appears to be irreversible, at least during the time of residence within the GIT. As a result, charcoal often reduces the extent of drug absorption. Indeed, this fact... 

D Fleisher, C Li, Y Zhou, L-H Pao, A Karim. Drug, meal and formulation interactions influencing drug absorption after oral administration. Clin Pharmaco-kin 36 233-254, 1999. 

The most commonly used methods for studies of partitioning into a membrane, mechanisms of drug absorption, and interactions with epithelial proteins, such as transporters and enzymes, are the cell culture-based models. These are both sim-... 

Johansson, O., Lindberg, T., Melander, A., Wahlin-Boll, E., Different effects of different nutrients on theophylline absorption in man, Drug Nutr. Interact. 1985, 3, 205-211. 

Interaction by food on the drugs adds additional variability and un-certainties to drug absorption and there are several classical examples of serious interactions (Table 8.4). 

Although this section deals mainly with the advantages of excised tissues with respect to nasal drug delivery studies, it is important to highlight some important attributes of nasal in situ perfusion model. Although this method does not provide data on systemic absorption, it enables study of the interactions of nasal mucosal enzymes, peptide substrates, and metabolic inhibitors and their implications for nasal drug absorption [13], It also enables the rate of nasal drug absorption to be determined. 

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