Tell your doctor right away if you have signs of blood vessel inflammation: flu-like symptoms, severe sinus pain, a skin rash, numbness or a "pins and needles" feeling in your arms or legs.
Stop taking  zafirlukast and call your doctor right away if you have any unusual changes in mood or behavior (such as agitation, confusion, depression, sleep problems, compulsive behaviors, hallucinations, or suicidal thoughts or actions).
Before taking this medicine
You should not use zafirlukast if you are allergic to it, or if you have liver disease (including cirrhosis).
Tell your doctor if you have ever had liver disease.
Not approved for use by anyone younger than 5 years old.
The chewable tablet may contain phenylalanine and could be harmful if you have phenylketonuria (PKU).
It is not known if zafirlukast will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.
You should not breastfeed while using zafirlukast.
How should I take zafirlukast?
Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.
Zafirlukast is not a fast-acting rescue medicine for asthma attacks. Seek medical attention if your breathing problems get worse quickly, or if you think your medications are not working.
Take on an empty stomach, at least 1 hour before or 2 hours after a meal.
Your dose needs may change due to surgery, illness, stress, or a recent asthma attack. Do not change your dose or stop using asthma medication without your doctor's advice.
Keep using zafirlukast as directed, even if you have no asthma symptoms.
If you take oral steroid medicine, do not stop it suddenly. Ask your doctor about tapering your dose.
Store at room temperature away from moisture, heat, and light. Keep the bottle tightly closed when not in use.
What happens if I miss a dose?
Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
