A New PAMPA Model Proposed on the Basis of a Synthetic Phospholipid Membrane

The purpose of this work was to investigate the synthetic phospholipid dependence of permeability measured by parallel artificial membrane permeability assay (PAMPA) method. Three phospholipids with hydrophobic groups of different lengths and phosphorylcholine as the hydrophilic group were concisely synthesized. Ten model drug molecules were selected because of their distinct human fraction absorbed (% FA) values and various pK(a) characteristics. In vitro drug permeation experiments were designed to determine the effect of the incubation time (4-20 h), pH gradient (4.6-9.32) and carbon chain length (8, 10, 12) on the drug permeability through the synthetic phospholipid membrane in the PAMPA system. The results showed that intensive and significant synthetic phospholipids dependence of permeability influenced by the length of lipid's hydrophobic carbon chain. The effective permeability constant (P-e) of each drug increased rapidly with time, then decreased slightly after reaching the maximum; the pH gradient changed the drug permeability according to the pH-partition hypothesis for drugs with diverse pK(a) values; and longer hydrophobic chains in the synthetic phospholipid membrane improved the drug permeability, as observed for all test drugs at almost all incubation time points. This newly proposed PAMPA model considered the synthetic phospholipid membrane and showed good P-e-% FA correlation for the passive transport of drugs, making it a helpful supplementary method for PAMPA systems.