Leukotriene antagonist

A leukotriene antagonist (sometimes referred to as a leukast) is a drug that inhibits leukotrienes, which are fatty compounds produced by the immune system that cause inflammation in asthma and bronchitis, and constrict airways.

Leukotriene inhibitors (or modifiers), such as montelukast, zafirlukast and zileuton, are used to treat those diseases. They are less effective than corticosteroids and thus less preferred in the treatment of asthma.

Approaches
There are two main approaches to block the actions of leukotrienes.

Inhibition of the 5-lipoxygenase pathway
Drugs such as zileuton block 5-lipoxygenase, inhibiting the synthetic pathway of leukotriene metabolism, whereas drugs such as MK-886 block the 5-lipoxygenase activating protein (FLAP) and may help in treating atherosclerosis.

Antagonism of cysteinyl-leukotriene type 1 receptors
Agents such as montelukast and zafirlukast block the actions of cysteinyl leukotrienes at the CysLT1 receptor on target cells such as bronchial smooth muscle.

These modifiers have been shown to improve asthma symptoms, reduce asthma exacerbations and limit markers of inflammation such as eosinophil counts in the peripheral blood and bronchoalveolar lavage fluid. This demonstrates that they have anti-inflammatory properties.