Eicosanoids are cell-signaling molecules produced from arachidonic acid. With the action of phospholipase A2, arachidonic acid is released from the plasma membrane. The different families of eicosanoids, which are prostaglandins (PGs), thromboxanes (TXA2s), prostacyclin (PGI2), lipoxins (LXs), and leukotrienes (LTs), emerge from a series of reactions catalyzed by different enzymes. The LTs and LXs are products of the lipoxygenase (LOX) pathway. The remaining eicosanoids are produced from the COX pathway, which involves 2 enzymes, COX-1 and COX-2. Eicosanoids are involved in various physiological and pathological processes. Thromboxanes cause platelet aggregation and are potent vasoconstrictors. Leukotrienes mediate allergic responses, while LXs have anti-inflammatory activities. Principal actions of PGs include vasodilation, smooth muscle contraction, and inflammation. Prostacyclin, a member of the PG family, has a potent vasodilatory effect. Both biologic actions and inhibitions of eicosanoids are mechanisms used in pharmacologic agents for various medical conditions and desired clinical effects.