Following injection, parecoxib sodium is rapidly converted to valdecoxib: the in vivo
pharmacology of parecoxib is therefore that of valdecoxib. The mechanism of action of
valdecoxib is by inhibition of cyclooxygenase-2 (COX-2)-mediated prostaglandin synthesis.
At therapeutic plasma concentrations in humans, valdecoxib does not inhibit
cyclooxygenase-1 (COX-1). In animal models, valdecoxib is anti-inflammatory, analgesic,
and antipyretic.