The eicosanoids (prostaglandins, thromboxanes, and leukotrienes) are synthesized from polyunsaturated fatty acids released from membrane phospholipids by phospholipase A2 . Glucocorticoids inhibit phospholipase A2 and thereby block production of all eicosanoids. NSAIDs inhibit COX, which converts arachidonic acid to prostaglandins and thereby block prostaglandin production. Because thromboxanes are derived from prostaglandins, NSAIDs also indirectly block thromboxane production. Leukotrienes, however, are produced from arachidonic acid by a different pathway (lipoxygenase) than prostaglandins and thereby are not blocked by NSAIDs. Leukotrienes are involved in asthma, so leukotriene inhibitors can be used to treat asthma.