Osteoarthritis (OA) is an autoimmune disorder which can be identified by chronic pain, inflammation, and impaired functionality. Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for the treatment of OA. Nonsteroidal anti-inflammatory drug (NSAID) patches are easy to use and suffer from less gastrointestinal side effects as compared to oral NSAIDs, but their percutaneous absorption is not enough to obtain a clinically efficient and satisfactory response. Evidence from animal and clinical studies indicates a dramatic improvement in percutaneous absorption by the inclusion of S-flurbiprofen plaster (SFPP).

A multicenter, randomized, double-blind, parallel-group comparative study was conducted to evaluate the efficacy, safety and optimal dose of SFPP in patients with knee OA. A total of 509 enrolled knee OA patients were either treated with placebo or SFPP at a concentration of 10, 20, or 40 mg. These three concentrations were applied to the affected site once daily for two weeks. The efficacy was analyzed using endpoints like improvement in knee pain on rising from the chair {primary endpoint assessed by visual analog scale (VAS)}, clinical symptoms, pain on walking, and global assessment by both investigator and patient. Safety was analyzed by determining the adverse effects associated with the administration of SFPP and placebo.

VAS scale analyzed changes in knee pain from baseline to trial end, and they were found to be dose-dependent. Least mean squares were 29.5, 31.5, 32.0, and 35.6 mm in the placebo and SFPP 10, 20, and 40 mg, respectively but significant differences were found between placebo and SFPP at the dose of 40 mg (P=0.001). There was no significant difference in the effect of SFPP observed at a dose ≤20 mg when compared with placebo. The percentage of the patients who achieved 50% pain relief was 72.4% in 40 mg and 51.2% in placebo (P<0.001). SFPP 40 mg showed significant improvement in all other points when compared with placebo. There were no differences in the incidence of adverse effects (AEs) among all four groups. Also, no severe AEs were reported.

All groups including placebo showed clinically important pain relief.  S-flurbiprofen plaster (SFPP) 40 mg showed exceptional pain relief. Pain relief was observed not only in primary endpoint but also in all the other parameters with significant differences over placebo. There were no differences observed in safety profile of SFPP from that of placebo. Therefore, SFPP 40 mg was discovered as the optimal tested dose for Knee OA management.