Evaluation of the carrier potential for the lipid dispersion system with lipophilic compound

KW-3902 (a newly synthesized adenosine A(1)-receptor antagonist) has potent diuretic and renal protective activities and was formulated in lipid dispersion systems, i.e., lipid emulsions and liposomes. The objective of the present study was to evaluate the carrier potential of these lipid dispersion systems, which is explained here as the ability of the formulation to retain the drug in its dispersed phase. The relative affinity of the drug to the formulation, K(f/b), was defined as a parameter in order to assess the performance of the formulations and was obtained from the in vitro blood component binding study. The results indicated that KW-3902 showed higher relative affinity to the liposome formulation than to the lipid emulsion. Moreover, the total amount of drug retained in the dispersion system depended on both K(f/b) and the dosing volume. The usefulness of the parameter, K(f/b), was discussed as an indicator for a carrier potential to understand the properties of the formulations.