ABSTRACT
Objective: To prepare capsaicin emulgel and investigate its transdermal delivery ability in vitro, analgesic effect and skin irritation. Methods: The effect of different penetration enhancers on the percutaneous permeation of emulgel in vitro was investigated by using the modified Franz diffusion cell. The optimal prescription was determined and the transdermal absorption of capsaicin emulgel was investigated; Analgesic effect was tested by hot plate method; The rabbit skin irritation test was used to evaluate the safety of capsaicin emulgel. Results: Peppermint oil, eucalyptus oil, and azone three kinds of penetration enhancers had no significant effect on enhancing permeation effect, so the final formulation of the emulgel was optimized without penetration enhancers. In vitro transdermal test showed that the cumulative permeation quantity of commercially available creams, self-made gels and emulgel was 18.98%, 37.04%, and 54.75%, respectively. In the hot plate method, the inhibitory rates of commercially available creams and high dose of emulgel after oral administration of 30, 60, and 90 min were 14.07%, 14.49%, 16.81%, 18.63%, 22.50%, and 25.57%. The skin irritation test results indicated that emulgel has no irritation to the rabbit skin. Conclusion: Capsaicin emulgel has good percutaneous permeability without skin irritation, the middle and high dose of emulgel have good analgesic activity, which will supply evidence for the selection for the local transdermal formulations of capsaicin.