Montelukast is an orally active compound that binds with high affinity and selectivity to the CysLT1 receptor (in preference to other pharmacologically important airway receptors, such as the prostanoid, cholinergic, or beta-adrenergic receptor). Montelukast inhibits physiologic actions of cysteinyl leukotriene LTD4 at the CysLT1 receptor without any agonist activity.