A mediator of Immediate Hypersensitivity . Leukotrienes are derived from the action of enzyme 5-lipoxygenase on arachidonic acid and are the chemicals which cause asthma symptoms.
Leukotriene modifiers such as Zileuton (a 5-lipoxygenase inhibitor), Zafirlukast and Montelukast prevent the synthesis or action of leukotrienes and thus, are often used to treat asthma.