Chitosan hydrogel as a base for transdermal delivery of berberine and its evaluation in rat skin.

Berberine is the main ingredient of Coptis spp. This study selected berberine as a model drug to design a transdermal delivery system for the treatment of cutaneous leishmaniasis. Berberine was incorporated into chitosan hydrogel to prepare ointments. The physicochemical properties of the ointments and the release profile of berberine were investigated. The results indicated that the viscosity of chitosan hydrogel increased with an increasing amount of lactic acid or EDTA. The effect of EDTA on the viscosity was greater than that of lactic acid. By differential scanning calorimetry (DSC) measurement, no interaction was found to occur between chitosan and the soluble berberine. The release rate of berberine was inversely proportional to ointment viscosity. In in vitro skin perfusion studies, only trace amounts of berberine permeated through the rat skin due to its low oil-water partition coefficient. Surfactants were used as penetration enhancers to increase the percutaneous absorption of berberine. Among the enhancers, benzalkonium chloride was found to be the most efficient. Additionally, Tween 80 could increase the loading amount of berberine in the skin.