Development and Evaluation of an Innovative S‐Flurbiprofen‐Diethylamine Emulgel With Superior Transdermal Delivery and Analgesic Activity

This study aimed to develop an innovative (S-flurbiprofen)-diethylamine (SFP-DEA) emulgel formulation via incorporating SFP as the active pharmaceutical ingredient within a carbomer 940 gel matrix. SFP-DEA emulgel was synthesized by dissolving SFP-DEA in the aqueous phase of an oil-in-water (O/W) emulsion, followed by dispersion into a carbomer 940 gel matrix. The physicochemical stability of SFP-DEA emulgel was evaluated via centrifuge, temperature swing test, high temperature, and long-term storage at ambient conditions. Ex vivo SFP transdermal delivery of SFP-DEA emulgel was evaluated using a Franz diffusion cell combined with excised rat skin. The in vivo analgesic activity and skin irritation test of SFP-DEA emulgel were evaluated using a mouse knee osteoarthritis model and healthy rats, respectively. Results demonstrated that SFP-DEA emulgel showed robust physicochemical stability and retain a final SFP content of 1.5% (w/w). Ex vivo transdermal study demonstrated that EMG5 (the emulgel optimized with laurocapram and menthol as penetration enhancers) achieved an 8-h cumulative SFP transdermal flux of 741.28 μg/cm² (44.23% of the administered dose), which is 27.94-fold higher than that of Loqoa (SFP tapes). In addition, SFP-DEA emulgel demonstrated rapid analgesic efficacy, with an 84.36% pain inhibition rate within 30 min in the osteoarthritis model, and elicited no signs of skin irritation in rats. In conclusion, the SFP-DEA emulgel developed herein exhibits high stability, enhanced transdermal delivery, preliminary analgesic activity, and favorable safety profiles, positioning it as a promising topical therapeutic candidate.