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Abstract
The purpose of this study was to investigate the use of solubility parameters for the prediction of gastrointestinal absorption sites and absorption durations of drugs.
Three-dimensional solubility parameters of drug substances were calculated using an advanced parameter set based on the group contribution methods of Fedors and Van Krevelen/Hoftyzer. The results of the calculations were illustrated via Bagley diagram and related to absorption data reported in the literature.
Solubility parameters of drugs which are known to be absorbed over a long period in human's digestive tract were found in a limited area within the Bagley diagram. From the three-dimensional solubility parameters of these substances, a region for optimal absorption with the centre coordinates delta(v)=20.3 (J x cm(-3))(0.5) and delta(h)=11.3 (J x cm(-3))(0.5) could be derived. Drugs with absorption sites along the whole gastrointestinal tract were found in this area. Drugs which are preferably absorbed from upper parts of the intestine are located in another typical region with partial solubility parameters delta(h) of more than 17 (J x cm(-3))(0.5).
The method which is presented in this paper appears as a simple but effective method to estimate the absorption behaviour of new substances in drug research and development.