Topical application of liposomally entrapped cyclosporin evaluated by in vitro diffusion studies with human skin

The kinetics and extent of uptake of cyclosporin (CSA) in various strata of human cadaver skin upon topical application of several CSA formulations were determined by in vitro diffusion cell experiments. The CSA formulations tested included an oil-in-water emulsion and four liposomal systems. The accumulation of CSA in the stratum corneum at 24 h is in the order: 'skin lipid' multilamellar liposomes (MLV) greater than phospholipid MLV approximately 'skin lipid' large unilamellar liposomes (LUV) greater than phospholipid LUV much much greater than emulsion. The total amount of drug in the deeper stratum corneum and deeper skin strata at 24 h is in the order: phospholipid MLV greater than 'skin lipid' MLV greater than phospholipid LUV greater than 'skin lipid' LUV greater than emulsion. Whereas 'skin lipid' liposomes were more effective than phospholipid-based liposomes in depositing drug in deeper skin strata for rodent species (mouse and guinea pig), the opposite effect was observed for human cadaver skin. More importantly, all the liposomal formulations tested were far more effective than the emulsion formulation in depositing CSA into the skin.