• Basic Info
• Top Questions
• Clinical Info
• Interactions

What is zafirlukast?
Zafirlukast 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. Zafirlukast is used to treat and prevent asthma attacks in adults and children as young as 5 years old. Do not give this medication to a child without a doctor's advice. Zafirlukast may also be used for other purposes not listed in this medication guide.

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What is the price of this medication and similar alternatives?

This pricing information is subject to change at the sole discretion of DS Pharmacy. For the most current and up-to-date pricing information, please visit drugstore.com.

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What are the possible side effects of zafirlukast?

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

Call your doctor at once if you have any of these serious side effects:

• worsening asthma symptoms;

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

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

Less serious side effects may include:

• headache;

• nausea, vomiting, diarrhea, stomach pain;

• weakness;

• dizziness;

• muscle pain; or

• fever, sore throat, cold symptoms.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

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How should I take zafirlukast?
Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label. Zafirlukast is usually taken once daily in the evening for prevention of asthma or allergy symptoms. Follow your doctor's instructions. Take zafirlukast on an empty stomach, at least 1 hour before or 2 hours after a meal. Do not use zafirlukast to treat an asthma attack that has already begun. It will not work fast enough to reverse your symptoms. Use only a fast-acting inhalation medication to treat an asthma attack. Talk with your doctor if any of your asthma medications do not seem to work as well in treating or preventing asthma attacks.

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What is the most important information I should know about zafirlukast?
Do not use zafirlukast to treat an asthma attack that has already begun. It will not work fast enough to reverse your symptoms. Use only a fast-acting inhalation medication to treat an asthma attack. Talk with your doctor if any of your asthma medications do not seem to work as well in treating or preventing asthma attacks. It may take up to several weeks of using this medicine before your symptoms improve. For best results, keep using the medication as directed. Talk with your doctor if your symptoms do not improve after several weeks of treatment.

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What happens if I miss a dose?
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

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What other drugs will affect zafirlukast?
Before using zafirlukast, tell your doctor if you are using any of the following drugs: aspirin; a blood thinner such as warfarin (Coumadin); tolbutamide (Orinase); erythromycin (E.E.S., E-Mycin, Ery-Tab, Erythrocin); theophylline (Elixophyllin, Respbid, Slo-Bid, TheoDur, and others); carbamazepine (Carbatrol, Tegretol); or phenytoin (Dilantin). This list is not complete and there may be other drugs that can interact with zafirlukast. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

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Can I take this if I am pregnant or trying to get pregnant or if I am breastfeeding?

Zafirlukast has been assigned to pregnancy category B by the FDA. Maternal toxicity and deaths in rats were seen at 800 times the maximum recommended human daily dose on a mg/m2 basis. There are no controlled data in human pregnancy. Zafirlukast is only recommended for use during pregnancy when benefit outweighs risk.

Zafirlukast is excreted into human milk. The manufacturer recommends that due to the potential for serious reactions in nursing infants, a decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.

Animal studies have shown potential for tumorigenicity in mouse and rat studies and increased sensitivity in neonatal rats and dogs to the adverse effects of zafirlukast.

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Who should NOT use this medication?

Known hypersensitivity to zafirlukast or any ingredient in the formulation.

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What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine. Overdose symptoms may include skin rash and upset stomach.

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What should I discuss with my healthcare provider before taking zafirlukast?
Do not use this medication if you are allergic to zafirlukast. Before using zafirlukast, tell your doctor if you are allergic to any drugs (especially aspirin), or if you have liver disease. You may not be able to use zafirlukast, or you may need dosage adjustments or special tests during treatment. The chewable tablet form of this medication may contain up to 0.842 milligrams of phenylalanine. Talk to your doctor before using this form of zafirlukast if you have phenylketonuria (PKU). FDA pregnancy category B. This medication is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

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Can I stop taking the medication if I feel better?
As a general rule, you should always take your medications exactly as prescribed and do not change the dosage or stop taking the medication without first discussing it with your healthcare provider.

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I am on so many medications; do I have to take them all?
This is called polypharmacy—many different medications being used at the same time by one person. Sometimes, being on multiple medications is acceptable and appropriate but at other times it may be problematic. If you are receiving your medications from multiple physicians you need to ensure that they all know what medications you are taking. The best way to do this is to make a list of all the medications you are currently using, including all nutritional supplements, homeopathic remedies, vitamins and over-the-counter drugs (if possible, also include all the diseases you have been diagnosed with). Give a copy to every doctor who takes care of you so they have it on file, this way they can avoid duplicating medications and perhaps even try to consolidate some. After every doctor's visit remember to update the list accordingly. Also, as much as you possibly can, try to use the same pharmacy to fill all your prescriptions, this way any potential drug interactions can be caught and averted.

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Where can I get more information?
More Information

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