Generic name: Zileuton.

Zyflo is an asthma controller. People with asthma naturally produce chemicals called leukotrienes, which cause the muscles in the airways to contract and the lung tissue to swell, resulting in difficulty breathing. Zyflo works by blocking the effects of leukotrienes.

Quick Facts About Zyflo


Used to help prevent asthma attacks and other breathing disorders. It is prescribed for long-term treatment and is not an airway-opening medication.

Zyflo Dosage

Take with meals and at bedtime. Must be taken on a regular basis to be effective, whether or not you have had any recent asthma attacks. Continue taking prescription even while using another medication to stop an attack.

  • Usual adult dose: 600 milligrams 4 times per day, once with each main meal and once at bedtime.
  • Usual child dose: 12 years and older — follow adult dosing instructions. Not generally prescribed for children under 12.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose; go back to regular schedule. Do not double doses.

Zyflo Side Effects

Overdose symptoms:

none reported. However, if you suspect an overdose, immediately seek medical attention.

More common side effects: generalized pain, headache, liver inflammation, nausea, upset stomach.

Less common Zyflo side effects: accidental injury, abdominal pain, chest pain, constipation, dizziness, fever, gas, general feeling of ill health, insomnia, itching, muscle stiffness, neck pain, nervousness, swollen lymph glands, urinary infections, vaginal inflammation, vomiting.


Combining Zyflo with certain drugs could cause dangerous side effects.

Inform your doctor before combining Zyflo with:

propranolol (Inderal); terfenadine (Seldane); theophylline (Theo-Dur and others); warfarin (Coumadin).

No known food/other substance interactions. 

Special Cautions

If pregnant or planning to become pregnant, inform your doctor immediately. Appears in breast milk; could affect a nursing infant.

No special precautions apply to seniors.

Not generally prescribed for children under 12 years.

  • Do not stop or cut down on any other asthma medication you are using unless your doctor recommends it.
  • Zyflo is not an airway-opening medication. You will still need an inhaler to stop an attack.
  • Contact your doctor immediately if you experience any muscle pain or weakness.
  • May cause liver inflammation. Inform your doctor immediately if the following symptoms appear: abdominal pain, nausea, fatigue, lethargy, dark urine, itching, flulike symptoms, yellowing of skin or whites of eyes, stomach or intestinal problems. Should not be used if you have liver disease or history of alcohol addiction.


HealthSurvey.org provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Zyflo side effects, please contact your healthcare provider