Zafirlukast is used to control and prevent symptoms (such as wheezing and shortness of breath) caused by asthma. Controlling symptoms of asthma helps you maintain your normal activities and cuts down on time lost from work or school.

This medication must be used regularly to be effective. It does not work right away and should not be used to relieve sudden asthma attacks. If an asthma attack occurs, use your quick-relief inhaler (such as albuterol, salbutamol) as prescribed.

Read the Patient Information Leaflet if available from your pharmacist before you start taking zafirlukast and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth without food as directed by your doctor, usually 2 times daily. Take zafirlukast on an empty stomach at least 1 hour before or 2 hours after meals. The dosage is based on your age.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day. Keep taking this medication even if you feel well. Do not increase your dose, use this drug more often, or stop using it without first consulting your doctor.

Get medical help right away if your asthma symptoms worsen or if you are using your quick-relief inhaler more than usual or more often than prescribed.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• mental/mood changes (such as trouble sleeping, agitation, hallucinations, depression, thoughts of suicide)
• signs of infection (such as sore throat that doesn't go away, fever, cough)
• numbness/tingling of arms/legs
• chest pain
• coughing up blood
• worsening shortness of breath
• muscle/joint pain
• swelling ankles/feet

This drug may rarely cause serious (possibly fatal) liver disease. Get medical help right away if you have any symptoms of liver damage, such as:

• nausea/vomiting that doesn't stop
• loss of appetite
• stomach/abdominal pain
• yellowing eyes/skin
• dark urine

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking zafirlukast, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• liver disease
• alcohol use

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Other medications can affect the removal of zafirlukast from your body, which may affect how zafirlukast works. An example is erythromycin, among others.

This medication can slow down the removal of other medications from your body, which may affect how they work. An example is warfarin, among others.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as liver/lung function) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

Avoid substances that can worsen breathing problems by causing irritation or allergic reaction, such as smoke, pollen, pet dander, dust, and mold.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).