Ethosomes for skin delivery of ropivacaine: preparation, characterization and ex vivo penetration properties

Ropivacaine, a novel long-acting local anesthetic, has been proved to own superior advantage. However, Naropin (R) Injection, the applied form in clinic, can cause patient non-convenience. The purpose of this study was to formulate ropivacaine (RPV) in ethosomes and evaluate the potential of ethosome formulation in delivering RPV transdermally. The RPV-loaded ethosomes were prepared with thin-film dispersion technique and the formulation was characterized in terms of size, zeta potential, differential scanning calorimetry (DSC) analysis and X-ray diffraction (XRD) study. The results showed that the optimized RPV-ethosomes displayed a typical lipid bilayer structure with a narrow size distribution of 73.86 +/- 2.40 nm and drug loading of 8.27 +/- 0.37%, EE of 68.92 +/- 0.29%. The results of DSC and XRD study indicated that RPV was in amorphous state when encapsulated into ethosomes. Furthermore, the results of ex vivo permeation study proved that RPV-ethosomes could promote the permeability in a high-efficient, rapid way (349.0 +/- 11.5 mu g cm(-2) at 12 h and 178.8 +/- 7.1 mu g cm(-2) at 0.5 h). The outcomes of histopathology study forecasted that the interaction between ethosomes and skin could loosen the tight conjugation of corneocyte layers and weaken the permeation barrier. In conclusion, RPV-ethosomes could be a promising delivery system to encapsulate RPV and deliver RPV for transdermal administration.