Influence of liposomal formulation parameters on the in vitro absorption of methyl nicotinate

In the present paper the influence of liposomal formulations on the in vitro absorption of methyl nicotinate (MN) taken as model drug was investigated. Special attention was paid to the possible correlations between the characteristics of the liposome formulation and its "in vitro" performances. The preparation of a set of MN containing liposomal formulations is described, differing for: soybean phosphatidylcholine (PC) concentration, lipid charge (by alternatively using cationic or anionic surfactants), vesicle size and viscosity. Liposomes were prepared as aqueous suspension or viscous gels prepared using the acrylic polymer carbomer. The "in vitro" determination of MN permeability when released from the different liposomal formulations was performed by using a Franz cell assembled with a synthetic sylastic/cellulose/sylastic multimembrane system. The results indicated that MN permeability was directly related to PC concentration, inversely related to liposome size and to vehicle viscosity and finally the liposome charge only slightly influenced the MN in vitro absorption.