Oral administration drug absorption after

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 role of droplet size on drug stability stems from the correlation between droplet size and surface area, and between surface area of droplets and exposure of drug to the aqueous media. If the drug is relatively insensitive to aqueous media, this may not be a major issue however, for the converse situation, development of emulsions with relatively coarser droplet size may offer improved drug stability. Nonetheless, this should be balanced with physical stability of the emulsion as well as the efLciency of drug absorption after oral administration (Toguchi et al., 1990). 

Caco-2 cells, especially the human intestinal epithelial cell line, have been proposed and used for the simulation and prediction of intestinal drug absorption after oral administration. These membranes of cells have useful properties for correlation with in vivo data such as enzymatic and transporter systems [24]. 

KINETICS OF DRUG ABSORPTION AFTER ORAL ADMINISTRATION... 

Oette, K., Kiihn, G., Romer, A., Niemann, R., Gundermann, K.-X, Schumacher, R. The absorption of dilinoleoyl-phosphatidylcholine after oral administration. Drug. Res. 1995 45 875-879... 

Chan K and Gibaldi M. Assessment of Drug Absorption after Oral Administration. J Pharm Sci 1985 74 388—393. 

Chan, K.K.H. and Gibaldi, M. Assessment of drug absorption after oral administration. Journal of Pharmaceutical Sciences 1985 74 388-393. 

After oral administration, intestinal absorption of the statins varies between 30% and 85%. All of the statins, except simvastatin and lovastatin, are administered as active ffhydroxy acids. Simvastatin and lovastatin are administered as inactive lactones that must be transformed in the liver to their respective ffhydroxy acids. There is extensive first-pass hepatic uptake of all statins, but they enter the liver by different mechanisms. Uptake of atorvastatin, pravastatin, and rosuvastatin is mediated by the organic anion transporter 2 (OATP2). The lipophilic lactone forms of simvastatin and lovastatin are thought to enter the liver by simple diffusion. Due to extensive first-pass hepatic uptake, systemic bioavailability of the statins and their hepatic metabolites varies between 5% and 30% of administered doses. Except for fluvastatin and pravastatin, the metabolites of all statins have some HMG-CoA reductase inhibitory activity. Under steady-state conditions, small amounts of the parent drug and its metabolites produced in the liver can be found in the systemic circulation. In the plasma, >95% of statins and their metabolites are protein bound with the exception of pravastatin and its metabolites (50% bound). 

Masaoka Y, Tanaka Y, Kataoka M, Sakuma S, Yamashita S (2006) Site of drug absorption after oral administration assessment of membrane permeability and luminal concentration of drugs in each segment of gastrointestinal tract. Eur J Pharm Sci 29 240-250... 

Bioavailability is the amount of drug in a formulation that is released and becomes available for absorption or the amount of the drug absorbed after oral administration compared to the amount absorbed after intravenous administration (bioavailability - 100%), judged from areas remaining under plasma drug concentration-time curves. 

---