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Zileuton (By mouth)

Zileuton (zye-LOO-ton)

Helps prevent and control asthma attacks. Zileuton immediate-release tablets (Zyflo®) were withdrawn from the U. S. market on February 12, 2008. Zyflo CR® is still available.

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You should not use this medicine if you have had an allergic reaction to zileuton, or if you have liver disease.

How to Use This Medicine:

Long Acting Tablet, Tablet

  • Your doctor will tell you how much medicine to use. Do not use more than directed.
  • Keep using any other asthma medicines your doctor may have prescribed for you. You should not use less or stop using your other medicines unless your doctor has told you to.
  • To control your asthma, you will need to use this medicine every day as ordered. It may take a few days or weeks before the medicine works. Keep using the medicine as your doctor ordered.
  • Take the extended-release tablet within one hour after your morning and evening meals.
  • Swallow the extended-release tablet whole. Do not crush, break, or chew it.

If a dose is missed:

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine:

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are using theophylline (Theo-Dur®), a blood thinner (warfarin, Coumadin®), terfenadine (Seldane®, Seldane-D®), or blood pressure medicines, such as propranolol (Inderal®), metoprolol (Lopressor®), atenolol (Tenormin®), or nadolol (Corgard®).

Warnings While Using This Medicine:

  • Make sure your doctor knows if you are pregnant or breastfeeding, or if you have a history of any liver disease (such as hepatitis). Tell your doctor if you drink alcohol.
  • This medicine helps prevent asthma attacks. For the medicine to work, you will need to use it every day, even when you are not having problems with your asthma. If your asthma does not get better or if it gets worse while you are using this medicine, tell your doctor.
  • Zileuton will not stop a severe asthma attack after it has started. Your doctor may give you a medicine to inhale that will work quickly for a severe attack. If you are already using an inhaler medicine and start to need that medicine more often or use the maximum number of puffs allowed in a day, tell your doctor.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
  • Call your doctor right away if you have pain in the right upper part of your stomach, yellowing of the skin or the whites of the eyes, itching, or if you feel unusually tired or like you have the flu. These may be signs of liver problems.
  • This medicine may cause some people to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed and have problems with sleep. If you or your caregiver notice any of these side effects, tell your doctor right away.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Dark-colored urine or pale stools.
  • Fever, chills, cough, sore throat, and body aches.
  • Increased wheezing or trouble with breathing.
  • Nausea, vomiting, loss of appetite, or pain in your upper stomach.
  • Restlessness, anxiety, feeling irritable, mood or behavior changes, or thoughts of hurting yourself or others.
  • Tightness in the chest.
  • Tremors.
  • Unusual dreams or trouble with sleeping.
  • Unusual tiredness or weakness.
  • Yellowing of your skin or the whites of your eyes.

If you notice these less serious side effects, talk with your doctor:

  • Headache, stuffy or runny nose.
  • Indigestion, upset stomach, or diarrhea.
  • Muscle pain.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 5/1/2020

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