The Use of Immobilised Artificial Membrane (IAM) Chromatography for Determination of Lipophilicity

This review discusses Immobilised Artificial Membrane (IAM) HPLC technique in terms of the structure of IAM phases, experimental methods, and information content. In a first part, the relations between pharmacokinetics and lipophilicity are discussed. Lipophilicity in n-octanol of ionisable compounds is shortly examined as a base for further discussion. Particular emphasis is placed on the meaning of phospholipids as partition phases and on the HPLC partitioning techniques. The next part presents structural information on IAM columns. The influence of experimental conditions on IAM-HPLC parameters is also examined. Particular attention is paid to the relations between IAM data and other lipophilicity parameters: IAM data are compared to lipophilicity in n-octanol and partition in liposomes. In the last part, the effectiveness of IAM data to predict bioactivity data is discussed in terms of relationships found with data of i) permeability across Caco-2 cells and passive intestinal absorption, ii) penetration across the blood-brain barrier, iii) pharmacokinetics, iv) various other pharmacological activities, and v) transdermal transport. Based on the studies reported, IAM-HPLC appears as a suitable technique to achieve data of partition in biomembranes. As compared to lipophilicity in n-octanol, IAM data for ionised compounds are distinctive. As compared to partition in liposomes, IAM technique is much faster and more reproducible.