- (GI-Gastrointestinal; Pgp- Permeability Glycoprotein; BBB- blood brain barrier; cLogP- partition coefficient; Log S- aqueous solubility; CYP- cytochrome P450 enzyme; TPSA- Topological Polar Surface Area). According to Lipinski rule and other variant, a potential drug for oral administration should have at least 5 Hydrogen bond donors, 10 Hydrogen bond acceptors, molecular weight less than 500, cLogP less than 5, at least 10 rotatable bonds, less than 140Ã…2 surface area [31]