Valdecoxib-d 3 serves as an internal standard for quantifying valdecoxib (IC50s: 0.005 and 140 µM for COX-2 and COX-1, respectively). It inhibits LPS-induced PGE2 production (IC50 = 0.89 µM) and reduces carrageenan-induced paw edema and adjuvant-induced arthritis in rats (ED50s: 10.2 and 0.032 mg/kg, respectively).