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Zyflo CR

Generic Name: zileuton (zye LOO ton)
Brand Name: Zyflo, Zyflo CR

Medically reviewed on Aug 20, 2018

What is Zyflo CR?

Zyflo CR is a leukotriene (loo-koe-TRY-een) inhibitor. Leukotrienes are chemicals your body releases when you breathe in an allergen (such as pollen). These chemicals cause swelling in your lungs and tightening of the muscles around your airways, which can result in asthma symptoms.

Zyflo CR is used to prevent asthma attacks in adults and children as young as 12 years old.

Zyflo CR may also be used for purposes not listed in this medication guide.

Important Information

Call your doctor at once if you have nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes). These may be early signs of liver problems.

Do not use Zyflo CR to treat an asthma attack that has already begun. It will not work fast enough. Use only a fast acting inhalation medication. Talk with your doctor if any of your asthma medications do not seem to work as well in treating or preventing attacks.

It may take up to a few weeks before your symptoms improve. Keep using the medication as directed even if you feel fine or have no symptoms. Having no asthma symptoms is a sign that the medication is working.

Avoid drinking alcohol. It may increase your risk of liver damage.

Call your doctor at once if you have any mood or behavior changes, anxiety, depression, or thoughts about suicide or hurting yourself.

Before taking this medicine

You should not use Zyflo CR if you are allergic to it, or if you have liver disease.

To make sure you can safely take Zyflo CR, tell your doctor if you drink large amounts of alcohol.

FDA pregnancy category C. It is not known whether Zyflo CR will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.

It is not known whether zileuton passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Do not give Zyflo CR to a child younger than 12 years old without medical advice.

How should I take Zyflo CR?

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Take Zyflo CR with a full glass of water.

Zyflo CR tablets and extended-release tablets contain the same amount of the drug, but they are not taken in the same way. Follow your doctor's instructions.

Zyflo CR tablets are usually taken 4 times daily, with meals and at bedtime. This medicine tablets may be swallowed whole or split in half to make swallowing easier.

Zyflo CR extended-release tablets are usually taken twice daily, within 1 hour after your morning and evening meals.

Do not crush, chew, or break an extended-release tablet. Swallow it whole. Breaking the pill may cause too much of the drug to be released at one time.

Do not use Zyflo CR to treat an asthma attack that has already begun. It will not work fast enough. Use only a fast acting inhalation medication. Talk with your doctor if any of your asthma medications do not seem to work as well in treating or preventing attacks.

It may take up to a few weeks before your symptoms improve. Keep using the medication as directed even if you feel fine or have no symptoms. Having no asthma symptoms is a sign that the medication is working.

Asthma is often treated with a combination of drugs. Use all medications as directed by your doctor. Read the medication guide or patient instructions provided with each medication. Do not change your doses or medication schedule without your doctor's advice, even if you have no asthma symptoms.

Call your doctor right away if you feel that this medicine is not working as well as usual, or if it makes your condition worse. If it seems like you need to use more of any of your medications in a 24-hour period, talk with your doctor.

You may need regular medical tests to be sure this medication is not causing harmful effects. Visit your doctor regularly.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include severe forms of some of the side effects listed in this medication guide.

What should I avoid while taking Zyflo CR?

Avoid situations or activities that may trigger an asthma attack.

Avoid drinking alcohol. It may increase your risk of liver damage.

Zyflo CR side effects

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

  • nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);

  • skin rash, bruising, severe tingling, numbness, pain, muscle weakness;

  • mood or behavior changes, anxiety, depression, or thoughts about suicide or hurting yourself; or

  • worsening asthma symptoms.

Less serious side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Zyflo CR?

Tell your doctor about all other medicines you use, especially:

This list is not complete and other drugs may interact with Zyflo CR. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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