In Silico PAMPA

The experimental Papp data have been used to build predictive models. However, since PAM PA is already a model, an in silico model based on this is a model of a model. The predictability for in vivo permeability or absorption of such in silico PAMPA model can be questioned (see Equation 5.11), since it is two steps from reality. 

Immobilized artificial membranes are another means of measuring lipophilic characteristics of drug candidates and other chemicals [105-109]. IAM columns may mimic membrane interactions better than the isotropic octanol/water or other solvent/solvent partitioning system. These chromatographic indices appear to be a significant predictor of passive absorption through the rat intestine [110]. 

A related alternative is called immobilizedliposomechromatography (I LC) [111,112]. Compounds with the same log P were shown to have very different degrees of membrane partitioning on ILC depending on the charge of the compound [112]. 

Another relatively new lipophilicity scale proposed for use in AD ME studies is based on micellar electrokinetic chromatography (MEKC) [113]. A further variant is called biopartitioning micellar chromatography (BMC) and uses mobile phases of Brij35 (polyoxyethylene(23)lauryl ether) [114]. Similarly, the retention factors of 16 beta-blockers obtained with micellar chromatography using sodium dodecyl sulfate 

Each of these scales produces a lipophilicity index related but not identical to octanol/water partitioning. 

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