Enhanced topical delivery of tetrandrine by ethosomes for treatment of arthritis.

The purpose of this work was to explore the feasibility of ethosomes for improving the antiarthritic efficacy of tetrandrine by topical application. It was found that tetrandrine was a weak base (pK(a) = 7.06) with pH-dependent partition coefficient. The spherical-shaped ethosomes were prepared by pH gradient loading method. Ex vivo permeation and deposition behavior demonstrated that the drug flux across rat skin and deposition of the drug in rat skin for ethosomes was 2.1- and 1.7-fold higher than that of liposomes, respectively. Confocal laser scanning microscopy confirmed that ethosomes could enhance the topical delivery of the drug in terms of depth and quantity compared with liposomes. The ethosomes were shown to generate substantial enhancement of therapeutic efficacy of tetrandrine on Freund's complete adjuvant-induced arthritis with regard to liposomes. These results indicated that ethosomes would be a promising carrier for topical delivery of tetrandrine into and across the skin.