Triamcinolone permeation from different liposome formulations through rat skin in vitro

The permeation of triamcinolone acetonide (TRMA) from various liposome formulations through rat skin was studied in vitro. The penetrated amount, permeability and intradermal retention of TRMA were compared among various lipid compositions, different vesicle sizes (0.2, 0.4 and 1 mu m), charges (positive, negative and neutral), as well as between multilamellar vesicles (MLV) and small unilamellar vesicles (SUV). All of the liposome formulations resulted in significantly higher flux and permeability of TRMA than a commercial TRMA ointment. The 'skin lipid' liposome provided the most effective transdermal delivery of incorporated TRMA. Presence or absence of cholesterol in the lipid bilayers did not reveal any difference in transdermal delivery of the associated TRMA. The flux and permeability of TRMA through skin were not influenced by the vesicle size of MLV, but was significantly increased by negative SUV. Intradermal retention of TRMA from positive MLV was significantly higher, while that from neutral SUV was significantly lower, than from other formulations. Liposomal lipid was not detectable on the receptor compartment. These results suggest that liposome itself may not penetrate through the skin, but that it does enhance the transfer of incorporated TRMA, Liposomal lipid composition is the most important factor affecting the efficiency of transdermal delivery of incorporated drugs, but was not correlated with its phase transition temperature.