Cyclooxygenase-1 vs. cyclooxygenase-2 inhibitors in the induction of antinociception in rodent withdrawal reflexes

Non-steroidal antiinflammatory drugs (NSAIDs) inhibit the cyclooxygenase (COX) enzyme and so they are effective analgesic, antiinflammatory and antipyretic drugs. The discovery of COX-2 led to the search for new NSAIDs with a selective action over this isoenzyme. The experiments performed to date have shown either more, less or no different efficacy of new COX-2 selective NSAIDs when compared to the non-selective inhibitors, probably because the comparison has not been performed under similar conditions. We have therefore compared the analgesic activity of six NSAIDs with different selectivity for the COX isoenzymes. The experiments were performed using the recording of spinal cord nociceptive reflexes in anaesthetised rats and in awake mice. The non-selective COX inhibitors, such as dexketoprofen trometamol, were effective in reducing nociceptive responses both in normal and monoarthritic rats (ED50s: 0.31 and 3.97 μmol/kg, respectively), and in mice with paw inflammation (12.5 μmol/kg, p