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Zileuton (Systemic)

Brand Names

In the U.S.-

  • Zyflo


  • Antiasthmatic (leukotriene inhibitor)


Zileuton (zye-LOO-ton) is used by patients with mild to moderate chronic asthma to decrease the symptoms of asthma and the number of acute asthma attacks. However, this medicine should not be taken to relieve an asthma attack that has already started.

This medicine is available only with your doctor's prescription, in the following dosage form(s):

  • Tablets (U.S.)

Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For zileuton, the following should be considered:

Allergies- Tell your doctor if you have ever had any unusual or allergic reaction to zileuton.

Pregnancy- Zileuton has not been studied in pregnant women. However, studies in rabbits have shown that this medicine causes problems when given in doses equal to the maximum human dose. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.

Breast-feeding- Zileuton passes into breast milk and may cause unwanted effects in nursing babies. Taking zileuton is not recommended while you are breast-feeding.

Children- Studies on this medicine have been done only in adult patients and there is no specific information comparing use of zileuton in children up to 12 years of age with use in other age groups.

Older adults- This medicine has been tested and has not been shown to cause different side effects or problems in older people than it does in younger adults.

Other medicines- Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking zileuton, it is especially important that your health care professional know if you are taking any of the following:

  • Beta-adrenergic blocking agents (acebutolol [e.g., Sectral], atenolol [e.g., Tenormin], betaxolol [e.g., Betoptic, Kerlone], bisoprolol [e.g., Zebeta], carteolol [e.g., Cartrol], labetalol [e.g., Normodyne], levobunolol [e.g., Betagan], metipranolol [e.g., Optipranolol], metoprolol [e.g., Lopressor], nadolol [e.g., Corgard], oxprenolol [e.g., Trasicor], penbutolol [e.g., Levatol], pindolol [e.g., Visken], propranolol [e.g., Inderal], sotalol [e.g., Sotacor], timolol [e.g., Blocadren, Timoptic]) or
  • Terfenadine (e.g., Seldane) or
  • Theophylline (e.g., Theo Dur) or
  • Warfarin (e.g., Coumadin)-Zileuton may increase the effects of these medicines

Other medical problems- The presence of other medical problems may affect the use of zileuton. Make sure you tell your doctor if you have any other medical problems, especially:
  • Active alcoholism or
  • Liver disease-The chance of serious side effects may be increased

Proper Use of This Medicine

Zileuton is used to prevent asthma attacks. It is not used to relieve an attack that has already started . For relief of an asthma attack that has already started, you should use another medicine. If you do not have another medicine to use for an attack or if you have any question about this, check with your health care professional.


Follow your doctor's orders or the directions on the label . The following information includes only the average doses of zileuton. If your dose is different, do not change it unless your doctor tells you to do so.

  • For oral dosage form (tablets):
    • For asthma:
      • Adults and children 12 years of age and older-600 milligrams (mg) four times a day.
      • Children up to 12 years of age-Use and dose must be determined by your doctor.

Missed dose-

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.


To store this medicine:

  • Keep out of the reach of children.
  • Store away from heat and direct light.
  • Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
  • Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

Precautions While Using This Medicine

To work properly, zileuton must be taken every day at regularly spaced times, even if your asthma seems better .

It is very important that your doctor check your progress at regular visits. Your doctor will want to have certain tests done regularly to see if side effects may be occurring in your liver without your knowing it .

Check with your health care professional if more inhalations (puffs) than usual of an inhaled, short-acting bronchodilator are needed to relieve an acute attack or if more than the maximum number of puffs of the bronchodilator prescribed for a 24-hour period are needed .

You may be taking other medicines for asthma along with zileuton. Do not stop taking or reduce the dose of the other medicines, even if your asthma seems better, unless you are told to do so by your health care professional .

Side Effects of This Medicine

Side Effects of This Medicine

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • Rare
    • Flu-like symptoms;  itching;  right upper abdominal pain;  unusual tiredness or weakness;  yellow eyes or skin 

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

  • More common
    • Nausea;  upset stomach 

  • Less common
    • Abdominal pain;  weakness 

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

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Last updated: Tue, 06 Jan 2009 00:20:03 GMT