Evaluation of paeonol skin-target delivery from its microsponge formulation: in vitro skin permeation and in vivo microdialysis.

The aim of the present study was to design a novel topical skin-target drug-delivery system, the paeonol microsponge, and to investigate its drug-release patterns in dosage form, both in vitro and in vivo. Paeonol microsponges were prepared using the quasi-emulsion solvent-diffusion method. In vitro release studies were carried out using Franz diffusion cells, while in vivo studies were investigated by microdialysis after the paeonol microsponges were incorporated into a cream base. In vitro release studies showed that the drug delivered via microsponges increased the paeonol permeation rate. Ex vivo drug-deposition studies showed that the microsponge formulation improved drug residence in skin. In addition, in vivo microdialysis showed that the values for the area under the concentration versus time curve (AUC) for the paeonol microsponge cream was much higher than that of paeonol cream without microsponges. Maximum time (Tmax) was 220 min for paeonol microsponge cream and 480 min for paeonol cream, while the half-life (t1/2) of paeonol microsponge cream (935.1 min) was almost twice that of paeonol cream (548.6 min) in the skin (n = 3). Meanwhile, in the plasma, the AUC value for paeonol microsponge cream was half that of the paeonol cream. Based on these results, paeonol-loaded microsponge formulations could be a better alternative for treating skin disease, as the formulation increases drug bioavailability by lengthening the time of drug residence in the skin and should reduce side-effects because of the lower levels of paeonol moving into the circulation.