The eicosanoids are an important group of endogenous fatty acid derivatives that are produced from arachidonic acid, a 20-carbon fatty acid lipid in cell membranes. Major families of eicosanoids include the straight-chain derivatives (leukotrienes) and cyclic derivatives (prostacyclin, prostaglandins, and thromboxane). Inhibitors of the eicosanoids are shown in Figure below.