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.
By inhibition of both peripheral and central COX-2, valdecoxib reduces the production of
prostaglandins that are important mediators of pain and inflammation. In animal models, the
analgesic activity of valdecoxib is not reversible by naloxone. Therefore, DYNASTAT
Injection is not expected to exhibit the potential for dependence, sedation or respiratory
depression seen with opioid analgesic agents.
When given at the recommended doses for management of acute pain, the onset of analgesia
was 7–14 minutes and reached a peak effect within 2 hours. After a single dose, the duration
of analgesia was dose and clinical pain model dependent, and ranged from 6 to greater than