The Comparison Effects of Analgesics Flunixin Meglumine and Ketoprofen in Pain induced by Peroxynitrite in Guinea-Pigs

Non steroidal anti inflammatory drugs (NSAIDs) are widely used to reduce inflammation, pain and fever. The present study was organized to induce an experimental inflammation in an animal model, using a putative biological oxidant, Peroxynitrite (ONOO-) and to study the effects of Flunixin meglumine and Ketoprofen on the pressure-induced pain. For this purpose, 24 male guinea pigs were divided into 4 groups each consisting of 6 animals. Three groups (groups 2, 3 and4) were injected Peroxynitrite and one group (the first: control) received physiological salt solution subcutaneously in the paw. After induction of a local inflammatory response, Flunixin meglumine (1mg/kg) and Ketoprofen (2 mg/kg) were injected to the second and third groups, 5 times with 12h intervals. The first and the fourth groups were injected saline solution in the same manner. Pressure analgesiometry was performed before and 1 hour after injections. The animals in all 3 groups treated with Peroxynitrite demonstrated an increased sensitivity to painful pressure (P<0.05). Both NSAIDs decreased the pain sensation dramatically after the 1st and the 2nd injections but, not after the 3rd, 4th and the 5th injections. The study suggested that NSAIDs may be helpful in reducing pressure-induced pain in animal model in early hours of the treatment, whereas the effect subsides over time and ends up after a few days. This effect may be of importance in humans who receive these kinds of drugs for a long period as they may not be effective in reducing pain after a while.