Nitridergic Modulation of COX-2 Efficacy

Pain is a common unpleasant sensory and emotional experience, in which are frequently used in their treatment the nonsteroidal anti-inflammatory drugs (NSAIDs). A group of agents with antipyretic, analgesic, and anti-inflammatory properties due to the inhibition of cyclooxygenase enzymes (COXs). Among these drugs there are a group of selective inhibitors of COX-2 named coxib that include to parecoxib, celecoxib, rofecoxib and etoricoxib. Pharmacological information on the mechanism of action of coxibs is insufficient to determine the analgesic and anti-inflammatory efficacy of these agents. There are contradictory reports regarding the antinociceptive effects of the various coxibs at the preclinical level as well as the nitridergic modulation of such actions. The objective of the present study was to evaluate the antinociceptive efficacy of parecoxib, rofecoxib, celecoxib, and etoricoxib using the formalin hind paw assay in mice and the possible contribution of the nitridergic system in the efficacy of COX-2 agents. Antinociception was assessed in a murine formalin assay using dose-response curves to coxibs before and after i.p. administration of 5 mg/kg of L-NAME. Coxibs produced dose-dependent analgesia and anti-inflammation. L-NAME administration reduced the analgesic and anti-inflammatory effectiveness of parecoxib, rofecoxib, celecoxib, and etoricoxib. These findings suggest that the effect of these agents, in addition to COX-2 inhibition, would be mediated by other mechanisms, among which nitridergic modulation would be compromised.