Leukotriene modifiers are a relatively new class of drugs designed to prevent asthma and allergic reactions before they occur. They target leukotrienes, which are chemicals that inflame the lining of airways and cause symptoms such as wheezing and shortness of breath.

These drugs are taken orally, in pill or granule form, one to four times daily to prevent the symptoms of chronic and mild-to-moderate persistent asthma. They are a long-term strategy and are not designed to treat an asthma attack once it has begun.

Leukotriene modifiers may be effective in preventing symptoms of hay fever (allergic rhinitis) in some people, though they have not been as widely used to treat that condition. As with asthma, these medications are taken daily to prevent the onset of hay fever symptoms, not to relieve symptoms once they have started. Research into other potential uses for leukotriene modifiers, including the prevention of other forms of allergic symptoms (such as hives), is ongoing.

Patients with liver disease and those taking anticoagulants (medications that reduce the ability of blood to form clots) are among those who may need close monitoring while taking leukotriene modifiers.