What They Are: Leukotriene modifiers are a class of asthma medications that are sometimes used in place of or in combination with inhaled steroids. Inhaled steroids are generally the preferred mode of asthma treatment. But, in people with mild persistent asthma, sometimes inhaled steroids do not provide adequate relief from asthma symptoms. In these cases, leukotriene modifiers, also known as leukotriene antagonists, may be added to the asthma management plan.
How They Work: This type of medicine is called a leukotriene modifier or leukotriene receptor antagonist. Leukotrienes are substances in our bodies thought to cause allergy and asthma symptoms. They are released by mast cells and are part of the inflammatory process. They are the primary reason why your airways tighten (which is called bronchoconstriction) during an asthma attack.
In addition, leukotrienes are responsible for one aspect of the changes to the airways seen in chronic asthma, that is extreme irritation of the airway smooth muscle. This irritability, which is referred to as airway hyperreactivity, is caused by eosinophils, which are attracted into the airways by leukotrienes. So, leukotrienes play a significant role in both acute asthma attacks, as well as some of the more long-term, chronic effects of asthma.
There are actually 2 types of leukotrienes. The first type acts mainly in conditions such as cystic fibrosis, inflammatory bowel disease, and psoriasis. The second type of leukotrienes, called cysteinyl-leukotrienes, is connected more with eosinophil and mast cell induced-bronchoconstriction in asthma. Leukotriene modifiers work to block the effects of leukotrienes in our bodies by binding to receptors on smooth muscle and other tissue in your airways, as well as by preventing their release from mast cells.
The Effects: Leukotriene modifiers can be useful in preventing asthma and allergy symptoms, although they are not considered to be as effective as inhaled steroids. They are only recommended for use in people with mild persistent or moderate persistent levels of asthma. They produce the following positive effects:
- Prevent bronchoconstriction (airway tightening)
- Prevent excess mucus production in the airways
- Prevent swelling of the airways (airway narrowing)
When these asthma medications are taken regularly, as prescribed, they can prevent asthma attacks from occurring.
Examples: At present, there are only 3 different brands of leukotriene modifiers. They are:
Comparison to Inhaled Steroids: Leukotriene modifiers are not as potent or as effective as inhaled steroids in treating asthma. So, especially for moderate persistent asthma and severe persistent asthma, inhaled steroids will continue to be the treatment of choice. But, even though they are completely safe, some people may not want to take inhaled steroids or may want to try an alternative. In those cases, leukotrienes offer another choice. They are also an option that can be used to add to inhaled steroids, though they are not the preferred option for combination therapy.
The other advantage leukotrienes offer is that they are an oral medicine that is swallowed by mouth, rather than inhaled. For very young children and even some adults, that can make them easier to take. Finally, leukotrienes treat both allergies and asthma, which can also be beneficial.
Other Important Facts: Leukotrienes have relatively few side effects. However, Zafirlukast interferes with the action of a bloodthinner called Coumadin, or Warfarin. So people who take both will need to be closely monitored by their doctors. Zafirlukast and Zileutin can both cause liver problems, so people taking either of these drugs need to watch for the following symptoms of hepatitis and let their doctors know right away if they have them:
- anorexia, or poor appetite
- abdominal pain
- nausea
- jaundice, a liver condition causing a yellowish skin & mucus membrane color
- pruritis, which is extreme itchiness of the skin
Doctors may also prescribe regular lab studies to monitor liver enzymes.
In Summary
Leukotriene modifiers offer a valuable option for asthma treatment in people with mild to moderate severity of asthma. However, they are generally not as effective as inhaled steroids and should not be the first line of defense in asthma management.
Sources: Berger, Abi. "Science Commentary: What are leukotrienes and how do they work in asthma?." BMJ 319(1999): 90. <http://www.bmj.com/cgi/content/full/319/7202/90> "Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma." NHLBI Guidelines for the Diagnosis and Treatment of Asthma. 28 Aug 2007. National Heart Lung and Blood Institute. 18 Dec. 2007 <http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf>
