Leukotriene Pathway Modifiers for Long-Term Control of Asthma

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Generic Name Brand Name
montelukast Singulair
zafirlukast Accolate
zileuton Zyflo

These medicines are available as pills and chewable tablets.

How It Works

Leukotriene pathway modifiers improve lung function and reduce asthma symptoms.

Why It Is Used

The U.S. National Asthma Education and Prevention Program (NAEPP) recommends leukotriene pathway modifiers as an alternative treatment for people who have mild or persistent asthma. Preferred medicines are inhaled corticosteroids with or without long-acting beta2-agonists. footnote 1

These medicines may be used along with inhaled corticosteroids to control mild persistent and moderate persistent asthma. They may be especially helpful for people whose asthma is triggered by exercise, aspirin, or allergies.

Different types of medicines are often used together in the treatment of asthma. Treatment for asthma depends on a person's age, his or her type of asthma, and how well the treatment is controlling asthma symptoms.

  • Children up to age 4 are usually treated a little differently than those 5 to 11 years old.
  • The least amount of medicine that controls the asthma symptoms is used.
  • The amount of medicine and number of medicines are increased in steps. So if asthma is not controlled at a low dose of one controller medicine, the dose may be increased. Or another medicine may be added.
  • If the asthma has been under control for several months at a certain dose of medicine, the dose may be reduced. This can help find the least amount of medicine that will control the asthma.
  • Quick-relief medicine is used to treat asthma attacks. But if you or your child needs to use quick-relief medicine a lot, the amount and number of controller medicines may be changed.

Your doctor will work with you to help find the number and dose of medicines that work best.

How Well It Works

Research shows that compared with a placebo , leukotriene pathway modifiers:

  • Reduced symptoms in adults. footnote 2
  • Improved lung function in children. There are conflicting reports on whether they improved symptoms. footnote 3

But leukotriene pathway modifiers do not work as well as inhaled corticosteroids. And adding leukotrienes to inhaled corticosteroids is probably not as effective as adding long-acting beta2-agonists to inhaled corticosteroids. footnote 2 , footnote 3

Side Effects

All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.

Here are some important things to think about:

  • Usually the benefits of the medicine are more important than any minor side effects.
  • Side effects may go away after you take the medicine for a while.
  • If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.

Common side effects of this medicine include:

  • Vomiting and diarrhea.
  • Headaches.

Leukotriene pathway modifiers can cause more serious problems such as mood changes, depression , hallucinations , and suicidal thinking. But this is rare.

In rare cases, zafirlukast and zileuton cause liver damage. If the liver is being affected by zafirlukast or zileuton, liver function tests will show increased liver enzyme levels in the blood, usually within the first 2 months of treatment.

Montelukast causes fewer side effects than other leukotriene pathway modifiers. It is less likely to affect the liver. So liver function monitoring is not needed.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

People who take zafirlukast and medicine (called a blood thinner) that prevents blood clots need to have their clotting times checked regularly. When used with blood-thinning medicine, zafirlukast can increase the risk of bleeding. Zafirlukast also may cause problems when taken with other medicines, such as blood pressure medicines, aspirin, and some seizure medicines. Before you take zafirlukast, make sure your doctor knows that you are taking any of those medicines.

People who are taking zafirlukast or zileuton need to have liver function tests several times during the first 6 months of treatment. People who are taking theophylline along with zileuton may need to take less theophylline.

People who take leukotriene pathway modifiers may be more likely to take their medicine regularly, because it can be taken orally and has a more immediate effect on symptoms than some other medicines such as inhaled corticosteroids.

Leukotriene pathway modifiers are not used to treat asthma attacks .

Taking medicine

Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.

There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed .

Advice for women

If you are pregnant, breastfeeding, or planning to get pregnant, do not use any medicines unless your doctor tells you to. Some medicines can harm your baby. This includes prescription and over-the-counter medicines, vitamins, herbs, and supplements. And make sure that all your doctors know that you are pregnant, breastfeeding, or planning to get pregnant.


Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. National Institutes of Health (2007). National Asthma Education and Prevention Program Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma (NIH Publication No. 08-5846). Available online: http://www.nhlbi.nih.gov/guidelines/asthma/index.htm.
  2. Dennis RJ, Solarte I (2011). Asthma in adults (chronic), search date April 2010. BMJ Clinical Evidence. Available online: http://www.clinicalevidence.com.
  3. Turner ST, et al. (2012). Asthma and other recurrent wheezing disorders in children (chronic), search date June 2010. BMJ Clinical Evidence. Available online: http://www.clinicalevidence.com.


ByHealthwise Staff

Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine

Adam Husney, MD - Family Medicine

Specialist Medical Reviewer Elizabeth T. Russo, MD - Internal Medicine

Current as ofApril 19, 2017