Effect of the combination of permeation enhancer and ion-pairs strategies on transdermal delivery of tofacitinib

The aim of the present study was to develop a tofacitinib (TOF) transdermal patch by the combination of ion-pairs and chemical permeation enhancer strategies. And a theory of controlled release of chemical permeation enhancers by counterion was proposed on the basis of in vitro skin permeation and skin retention study. Through the in vitro skin permeation study, the formulation factors such as counterion, pressure sensitive adhesive (PSA), drug loading and patch thickness were investigated, and the optimized patch (6.5% LA-TOF, 15% POCC and thickness = 50 μm) was evaluated by the pharmacokinetic study. The AUC0-t of the optimized patch was 529.89 ± 45 h ng/mL. Special attention has been paid to the molecular mechanism of the effects of counterion concentration on the release and permeation enhancement effect of penetration enhancer. FTIR study, 13C NMR, XPS and molecular modeling were conducted to investigate the molecular interaction between POCC and LA. Raman Imaging and ATR-FTIR were used to explore the POCC content in the skin and the interference degree to lipid. The results revealed that a strong hydrogen bond appeared between LA and the hydroxyl group of POCC, which inhibited the release of POCC, thus reducing the lipid disturbance and permeation enhancement effect of POCC. In conclusion, this TOF patch was successfully developed. The effect of counterion on permeation enhancers was clarified at molecular level, and these results provided references for the development of TOF patch.