4,5-Dihydro-5-methyl-d3-3,4-diphenyl-5-isoxazolol is the labeled analogue of 4,5-Dihydro-5-methyl-3,4-diphenyl-5-isoxazolol (D449170), an intermediate for the preparation of Valdecoxib (V090000), a nonsteroidal anti-inflammatory drug (NSAID) that exhibits anti-inflammatory, analgesic and antipyretic properties in animal models. An inhibitor of prostaglandin synthesis primarily through inhibition of COX-2.