S(+)-Flurbiprofen Shows Potent PGE2 Inhibitory Activity in Inflammatory Cells, Superior Cell Transport Activity and Skin Permeability

We developed a novel topical non-steroidal anti-inflammatory drug (NSAID)patch, S(+)-flurbiprofen plaster, (SFPP), containing S(+)-flurbiprofen (SFP), an enantiomer of flurbiprofen (FP). In a previous study conducted in an animal model, we showed good skin absorption and potent analgesic efficacy of SFPP. In this study, to examine the superior features, as an NSAID patch, of SFP as compared to FP and R(-)-flurbiprofen (RFP), we tested the stereospecificity of SFP actions on Prostaglandin E2 (PGE2) inhibition in rat inflammatory leukocytes and in the binding activity of the drug to cells, and also the in vitro skin permeability of the drug in the Yucatan micropig (YMP). SFP showed potent inhibitory activity on PGE2 production from peritoneal leukocytes stimulated with a bacterial suspension, as compared to RFP and FP. The half maximal (50%) inhibitory concentration (IC50) values were 14 nM for SFP, 52 nM for FP, and 17,000 nM for RFP. In the cell binding study, significant and rapid increase of SFP binding to polymorphonuclear leucocytes (PMNs) was observed at 5 min after incubation, eventually reaching a steady state. SFP showed significantly higher binding activity for the inflammatory leucocytes as compared to RFP, suggesting its superior transfer potency. The skin permeability profile of SFP, RFP and FP in the YMP model showed that the rank order of the cumulative amount of permeated compounds in the skin was SFP > RFP > FP. The steady-state permeation rate (Flux) of SFP was significantly higher than that of FP (4.89 and 1.55 mg/cm2/h, respectively, p = 0.0068), indicating the remarkably superior skin permeability of SFP. SFP exerted potent inhibitory activity on PGE2 production and superior binding activity to the PMNs and skin permeability, as compared to FP and RFP. These results suggest that SFP possesses favorable characteristics for use as an active ingredient in the NSAID patch.