Overview Snapshot A 30-year-old woman presents to an asthma specialist for management of her moderate-to-severe asthma. She is currently using fluticasone and salmeterol inhalers. She continues to experience 2-3 episodes of asthma exacerbations a week with night-time awakenings and several trips to the emergency room in the past month. Her physician considers adding a targeted therapy that inhibits leukotrienes to her regimen. Introduction Arachidonic acid pathway transforms arachidonic acid into a variety of inflammatory mediators, including leukotrienes, prostacyclin, and prostaglandins Many anti-inflammatory agents, including asthma medications, target downstream molecules in this pathway Lipoxygenase pathway products LTB4 ↑ neutrophil chemotaxis LTC4, LTD4, and LTE4 ↑ bronchial tone montelukast and zafirlukast inhibit these products Prostacyclin PGI2 ↓ platelet aggregation vasodilation epoprostenol is a PGI2 analogue Prostaglandins PGE1 vasodilation also known as alprostadil used to maintain a patent ductus arteriosus in newborns with ductal-dependent congenital heart disease PGE2 ↑ uterine tone dinoprostone is a PGE2 analogue PGF2α ↑ uterine tone carboprost is a PGF2α analogue Thromboxane TXA2 ↑ platelet aggregation ↑ vasoconstriction