Tepoxalin is a dual inhibitor of COX and 5-lipoxygenase (5-LO; IC50s = 2.84 and 0.15 µM, respectively, in RBL-1 cell lysates). It also inhibits the activity of 12-, but not 15-, LO (IC50s = 4.45 and 146.6 µM for the human platelet and rabbit reticulocyte enzymes, respectively). Tepoxalin reduces the production of thromboxane B2 and leukotriene B4 induced by the calcium ionophore A23187 in human peripheral blood mononuclear cells (PBMCs; IC50s = 0.01 and 0.07 µM, respectively) and decreases epinephrine-induced platelet aggregation in human platelet-rich plasma (PRP; IC50 = 0.045 µM). It inhibits paw swelling in a rat model of adjuvant-induced arthritis with an ED50 value of 3.5 mg/kg.