Comparison of the Anti-Inflammatory and Analgesic Effects in Rats of Diclofenac-Sodium, Felbinac and Indomethacin Patches

BACKGROUND Topically applied nonsteroidal anti-inflammatory drugs (NSAIDs) are used widely for the treatment of pain and inflammation in musculoskeletal disorders. This study compared the analgesic and anti-inflammatory effects of patches of 1% diclofenac-sodium, 3.5% and 0.5% felbinac and 3.75% indomethacin in rats using the carrageenan-induced paw pad edema model and the brewer's yeast-induced hyper algesia model. Two studies were conducted: in the preliminary study, the patch was removed at 2 or 24 hrs after application, and in the main study the patch was removed at 2 hrs. The volume of the right hind paw and the pain threshold were assessed at 1, 3, 5, and 7 hrs after induction of inflammation in both studies. RESULTS In the main study, the edema ratio in the 1% diclofenac group at 5 hrs after induction of inflammation and the AUEC (Area Under the Effect Curve) were significantly lower than in the control animals (p=0.009). The edema suppression rate in the 1% diclofenac group (12.1-33.2%) was higher than in the 3.5% and 0.5% felbinac and 3.75% indomethacin groups. The pain threshold ratio did not decrease in the 1% diclofenac group and it was significantly higher than in the control group at 3 (p=0.0004) and 5 hrs (p=0.029). The 1/AUEC was significantly lower than that in the control group (p=0.004) and the lowest among all the NSAID groups. CONCLUSIONS This study demonstrated that the analgesic and anti-inflammatory effects of the 1% diclofenac sodium patch in a rat model may be exerted more promptly and persistently than with the 3.5% and 0.5% felbinac and 3.75% indomethacin patches.