Leukotriene modifiers (also known as leukotriene antagonists) are a relatively new class of drugs designed to prevent asthma and allergic reactions before they occur. They work by blocking the effects of leukotrienes, the chemicals involved in triggering asthma- and allergy-related symptoms.

Leukotriene modifiers work by either inhibiting leukotriene production or preventing leukotrienes from binding to cellular receptors, the cell components that combine with a drug, hormone or chemical mediator to alter the function of a cell. During an asthma attack, immunoglobulin E (IgE) destabilizes mast cells in the airway. When this happens, the mast cells release a group of chemicals – including histamines, prostaglandins and leukotrienes – that act as powerful bronchoconstrictors, narrowing airways and making breathing more difficult.

Leukotriene modifiers help short-circuit the process by targeting leukotrienes, which have a constricting effect that is 1,000 times more powerful than histamines and prostaglandins. They block the primary binding site on a cell membrane where leukotrienes bond. Blocking these cell receptors prevents the production of two of the three most powerful leukotriene bronchoconstrictors.

By shutting down the work of leukotrienes, leukotriene modifiers decrease inflammation and relax the smooth muscle around the bronchi. This prevents the body from going into an allergic response and keeps a person’s airways open and clear.

Leukotriene modifiers now in common use include:

Leukotriene modifiers can be taken in pill, chewable-tablet or granule form. These pills are taken one to four times daily, depending on which medication is used. Individuals who have been prescribed leukotriene modifiers should take the medication as directed by their physician, even when they are feeling well.

Leukotriene modifiers sometimes are prescribed to work in tandem with other asthma drugs. In some cases, patients with mild-to-moderate asthma who take leukotriene modifiers are able to reduce their reliance on other asthma drugs such as beta 2 agonists (short-acting bronchodilators that relax smooth muscle in the airways) and corticosteroids (anti-inflammatory drugs used to treat allergies and asthma). By reducing the frequency or doses of such medications, the risk of potentially serious side effects is also reduced.

Leukotriene modifiers may take several weeks to begin working, and in some people they are not effective at all. Patients taking leukotriene modifiers should consult their physician if their symptoms worsen or if they need to increase the use of their rescue medications.