Triptolide nanoemulsion gel as a transdermal drug delivery system: preparation, pharmacokinetics, and rheumatoid arthritis evaluation.

Purpose: This study aimed to develop and evaluate triptolide nanoemulsion gels (TP-NE gels) as a transdermal drug delivery system.

Methods: TP-NE was prepared and optimized via emulsification and the central composite design response surface method. The optimized TP-NE gel was evaluated in vitro and in vivo. TP-NE gel microstructure, in vitro and in vivo pharmacokinetics, and anti-rheumatoid arthritis effects were studied to evaluate the feasibility of its percutaneous administration.

Results: The Optimized TP-NE was observed using a Malvern Autosizer Nano ZS 90 inspection system and a transmission electron microscope (TEM). The nanoemulsion had an average size of 162.9 ± 0.281 nm, a polydispersity index of 0.272 ± 0.024, a zeta potential of -30.03 ± 2.01 mV, and mostly spherical and uniform morphology. In addition, the TP-NE gel pharmacokinetics, assessed via a skin-blood two-site synchronous microdialysis, revealed that TP was higher in the skin than in the blood. TP-NE gel is crucial in reducing knee edema, inhibiting inflammation, and treating rheumatoid arthritis by regulating tumor necrosis factor-alpha, interleukin-1β, and -6 levels.

Conclusion: The TP-NE gel is a promising local delivery method for rheumatoid arthritis (RA)-associated edema and inflammation and can serve as a prospective platform for percutaneous TP administration.