Objective:To study the enhancing effects of electret on transdermal delivery of lidocaine patches in vitro.Methods:In vitro rat skin permeation experiment was carried out with lidocaine patches,lidocaine paches with azone,positive/negative electret lidocaine patches,and positive/negative electret lidocaine patches with azone by using Franz diffusion cells.The accumulated lidocaine concentrations in rat skin treated with each kind of patches were examined by HPLC to investigate the influence of electret on transdermal delivery of lidocaine.Results:(1) The enhancement rates of 1%,3% and 5% azone lidocaine patches 10 h after application were 1.06,1.10 and 1.66 folds (P<0.05,5% azone vs lidocaine patch group) that of the lidocaine patch,respectively.(2) Lidocaine patches with negative electret containing 1%,3% and 5% azone showed similar transdermal behavior to the corresponding chemical enhancer patches.(3) Lidocaine patches with positive electret containing 1%,3% and 5% azone showed much better enhancing effect than the corresponding chemical enhancer lidocaine patches (P<0.05). Besides,5% azone together with positive electret showed a cooperative enhancing effect.Conclusion:Positive electret patch has better effect in enhancing transdermal delivery of lidocaine.Besides,the cooperative enhancing effect of azone with positive electret on transdermal delivery of lidocaine is in a concentration-dependent manner with azone.