The diffusion of prepared films was measured using a Franz diffusion cell apparatus (Microette Plus; Hanson Research, Chatsworth, CA, USA).23 After hair removal, skin (2 cm2) was collected from the abdominal area of male rats for use as a membrane. Each diffusion cell contained a donor and receptor chamber separated by a film. Phosphate-buffered saline was used as the receptor medium (pH 7.2), temperature was held at 32 ± 0.5°C and the stirring rate was 400 rpm. At 0.5, 1, 2, 4, 8, 12 and 24 h, the autosampler obtained aliquots, which were then analyzed using HPLC. The in vitro skin permeation data were used to measure skin permeation parameters such as steady-state transdermal flux (Jss), diffusion coefficient (D) and permeability coefficient (Kp). As a function of time, the total volume of OFI permeated per unit area of skin was plotted. The autosampler collected aliquots at 0.5, 1, 2, 4, 8, 12 and 24 h, and these were then analyzed by HPLC.24 Skin permeation parameters, steady-state transdermal flux (Jss), permeability coefficient (Kp) and diffusion coefficient (D).