Leukotrienes are inflammatory mediators and they have been implicated in asthma and allergic rhinitis. Leukotriene antagonists block leukotriene receptors. Leukotrienes are released from the nasal passages in people with allergic rhinitis contributing to swelling of the mucous lining of the nose causing discharge and a blocked nose.

Montelukast is an example of a leukotriene antagonist. This drug is typically taken once a day in the evening and can be swallowed as tablet or dispersed in a liquid. When used to treat asthma Leukotriene antagonists are typically used in step 4 (asthma treatment) or they can be used earlier (Step 2) in young children where the parents are keen to avoid inhaled steroids.