Computational Models for Prediction of Intestinal Permeability

Passive diffusion through the lipid bilayer of the epithelium can be described using the partition coefficient between octanol/water (log P) and A log P (the difference between the partition into octanol/water and heptane/ethylene glycol or heptane/ octanol) [157, 158], The lipophilicity of the drug (log P) (or rather log D at a certain pH) can easily be either measured or calculated, and is therefore generally used as a predictor of drug permeability. Recently, a method using artificial membrane permeation (PAMPA) has also been found to describe the passive diffusion in a similar manner to the Caco-2 cell monolayers [159]. 

The direct relationship between permeability and lipophilicity appears to reach a plateau at around log P of 2 [102, 117]. Therefore, permeation through the lipid 

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