INFLUENCE OF LIPOSOMAL FORMULATION PARAMETERS ON THE IN-VITRO ABSORPTION OF METHYL NICOTINATE

In the present study the influence of liposomal formulations on the in vitro absorption of methyl nicotinate (MN) taken as model drug was in vestigated. Special attention was paid to the possible correlations be tween the characteristics of the liposome formulation and its 'in vitr o' performance. The preparation of a set of MN-containing liposomal fo rmulations is described; these differ in soybean phosphatidylcholine ( PC) concentration, lipid charge (by using either cationic or anionic s urfactants), vesicle size and viscosity. Liposomes were prepared as aq ueous suspensions, or as viscous gels using the acrylic polymer carbom er. The in vitro determination of MN permeability when released from t he different liposomal formulations was performed using a Franz cell a ssembled with a synthetic silastic/cellulose/silastic multimembrane sy stem. The results indicated that MN permeability was directly related to PC concentration and inversely related to liposome size and to vehi cle viscosity; the liposome charge only slightly influenced the in vit ro absorption of MN. (C) 1998 Elsevier Science B.V. All rights reserve d.