Eicosanoids include prostaglandins (PG), thromboxanes (TX), leukotrienes (LT), and lipoxins (LX). Prostanoids refer to PGs and TXs. The names of prostanoids are given according to the number of carbon-carbon double bonds in the molecule. Because of the presence of two carbon-carbon double bonds, most of the biologically active prostaglandins and thromboxanes are series 2 molecules. The eicosanoids with four carbon-carbon double bonds are series 4 molecules. Eicosanoids