Parecoxib Impurity 12 Parecoxib Impurity 23 Parecoxib Impurity D Parecoxib Impurity 18 4-(3-methyl-4-phenylisoxazol-5-yl)benzenesulfonamide Parecoxib SodiuM iMpurity D Parecoxib Impurity 3 Parecoxib Impurity 22 Parecoxib Sodium Impurity H Parecoxib Impurity 17 Parecoxib Impurity 13 Parecoxib Impurity 21 5-Methyl-3,4-diphenylisoxazole Parecoxib Impurity 16 Parecoxib Sodium Imp.E Valdecoxib IMpurity D Parecoxib Impurity 14 Parecoxib Impurity 20