Zafirlukast
Zafirlukast is a prescription oral tablet used for the long-term prevention and management of asthma in adults and children aged 5 and older.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 7 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
📖 Zafirlukast: Patient Information Guide
A plain-language walkthrough of Zafirlukast — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Zafirlukast tablets are approved for the ongoing prevention and management of asthma. Here's what the evidence supports:
- Prevention and chronic treatment of asthma in adults and children 5 years of age and older
- Reducing airway swelling and tightness that cause ongoing asthma symptoms
- Helping control response to asthma triggers such as allergens, cold air, and sulfur dioxide
- Not approved for relieving sudden (acute) asthma attacks or status asthmaticus — this applies to all supported tablet products
⚙️How it works▾
Asthma involves the release of inflammatory chemicals called leukotrienes (particularly LTD4 and LTE4), which cause the airways to swell, fill with fluid, and tighten up. People with asthma are dramatically more sensitive to these chemicals than people without it. Zafirlukast selectively blocks the receptors that these leukotrienes attach to, preventing them from triggering airway constriction and inflammation. The result is less swelling, less tightening, and calmer airways over time.
Research shows zafirlukast can reduce airway responses to both early triggers (immediate reactions) and delayed reactions (late-phase responses) to inhaled allergens like cat dander, ragweed, and grass pollen. It also reduces overall airway hypersensitivity (how easily the airways overreact to irritants).
💊How it's taken▾
Zafirlukast tablets are taken by mouth twice a day. Because food can reduce how much drug your body absorbs, take it at least 1 hour before or 2 hours after a meal. Dosing differs by age group — adults and children 12 and older have one schedule, while children ages 5 through 11 follow a separate lower-dose schedule; follow your prescription exactly. Elderly patients (65+) may have higher drug levels in their blood, but standard dosing has been used without a notable increase in side effects in clinical trials.
- Do not double up if you miss a dose — take it as soon as you remember, unless it's almost time for your next dose
- Do not stop taking zafirlukast during an asthma flare-up without talking to your doctor first
🤒Side effects — in detail▾
Most people tolerate zafirlukast well, but some side effects do occur. Common ones include:
- Headache
- Nausea, diarrhea, or upset stomach
- Abdominal (stomach) pain
- Vomiting
- Dizziness
- Muscle aches (myalgia)
- General weakness or fatigue
- Elevated liver enzymes (seen on blood tests)
Serious reactions — including liver damage, severe allergic reactions (hives, swelling, rash with blistering), mood changes such as depression or insomnia, and a rare inflammatory condition called Churg-Strauss syndrome — require immediate medical attention. Stop taking zafirlukast and call your doctor right away if you develop yellowing of the skin or eyes, severe fatigue, or right-sided upper abdominal pain.
⚠️Warnings & precautions▾
- Liver failure: Rare but life-threatening liver damage has been reported, including cases requiring transplant or resulting in death. Watch for right-sided stomach pain, fatigue, jaundice (yellow skin or eyes), nausea, or flu-like symptoms. Stop the drug and see a doctor immediately if these occur. Zafirlukast is contraindicated in anyone with existing liver disease.
- Not for acute asthma attacks: Zafirlukast will not stop a sudden asthma attack. Always keep a quick-relief (rescue) inhaler available.
- Warfarin interaction: Zafirlukast significantly raises warfarin blood levels, increasing the risk of dangerous bleeding. Close monitoring of blood clotting is required if you take both.
- Churg-Strauss syndrome: Rarely, people with asthma on zafirlukast develop a serious inflammatory condition (Churg-Strauss syndrome) causing eosinophilia (high white blood cell counts), rash, and organ involvement. Report worsening respiratory symptoms, skin rashes, or neurological changes to your doctor.
- Neuropsychiatric effects: Insomnia and depression have been reported. Tell your doctor if you notice mood or sleep changes.
- Infections in older adults: Clinical trials showed a higher rate of mostly mild respiratory infections in patients over 55 — especially those also taking inhaled corticosteroids.
🔀What it interacts with▾
Zafirlukast affects liver enzymes (mainly CYP2C9 and CYP3A4) that process many medications, which can raise or lower drug levels in your blood. Key interactions include:
- Warfarin: Zafirlukast can raise warfarin levels significantly, increasing bleeding risk — regular blood clotting (PT) monitoring is essential
- Erythromycin: This antibiotic can reduce zafirlukast levels by about 40%, potentially reducing its effectiveness
- Theophylline: Can lower zafirlukast levels; rare reports of zafirlukast raising theophylline to toxic levels have also been noted
- Aspirin: Can raise zafirlukast blood levels by about 45%
- Fluconazole and other CYP2C9 inhibitors: Can raise zafirlukast levels — fluconazole raised them by about 58% in one study
- Phenytoin, carbamazepine, tolbutamide: No formal studies done, but caution is advised as zafirlukast affects the same enzyme that processes these drugs
- Cyclosporin, calcium-channel blockers, and other CYP3A4 substrates: Zafirlukast inhibits this enzyme in lab studies; clinical monitoring is recommended when used together
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- Allergy to zafirlukast: Do not take it if you've ever had an allergic reaction to zafirlukast or any of its ingredients
- Liver disease or cirrhosis: Zafirlukast is contraindicated — the drug accumulates to dangerous levels and serious liver events are more likely
- Children under 5: Not approved for this age group
- Adults 65 and older: Drug levels can be about twice as high as in younger adults — your prescriber should be aware, though standard doses have been used in trials without notable extra risk
- Kidney disease: No dose adjustment is needed for patients with kidney (renal) impairment based on available data
- Other medications: Tell your prescriber and pharmacist about all drugs you take — especially warfarin, theophylline, erythromycin, phenytoin, aspirin, and antifungals
- Pregnancy and breastfeeding: Discuss with your doctor before taking zafirlukast if you are pregnant, planning to become pregnant, or breastfeeding
🚑If you take too much▾
Overdose with zafirlukast has been reported in a small number of patients. The main symptoms were rash and upset stomach, and no consistent serious toxic effects were observed. If an overdose is suspected, standard supportive care is recommended — including removing any unabsorbed drug and monitoring the patient — and medical attention should be sought promptly.
📡Pharmacodynamics — effects in the body▾
Zafirlukast works by blocking leukotriene receptors in the airways, which prevents chemicals that cause airway narrowing and inflammation from doing their job. In people with asthma, this translates to reduced airway swelling, less smooth muscle tightening, and a blunted response to triggers like allergens, cold air, sulfur dioxide, and histamine. Studies show it reduces both the immediate and delayed airway reactions to inhaled allergens, and it lowers overall airway hypersensitivity (the tendency to overreact to irritants).
🔬Pharmacokinetics — how your body processes it▾
Zafirlukast is absorbed quickly after a tablet is swallowed, with blood levels peaking around 3 hours after a dose. Food can reduce absorption by about 40%, which is why it must be taken away from meals. It is extensively broken down by the liver (primarily through the CYP2C9 enzyme pathway), and most of the drug is eliminated through the feces, with only about 10% leaving through urine. The drug's half-life (the time it takes for half the drug to leave the body) is roughly 8 to 16 hours, and it reaches steady levels in the blood with twice-daily dosing.
📦How to store it▾
Store at 20°-25°C (68°-77°F) . Protect from light and moisture. Dispense in air-tight container.
📄 Written from Zafirlukast’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Zafirlukast
88 supplements and herbal products have documented interactions with Zafirlukast in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 1
- Moderate · 64
- Minor · 23
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Zafirlukast — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly does zafirlukast do — is it the same as an inhaler? ▾
Does it matter when I take it — can I just take it with breakfast? ▾
What side effects should I actually watch out for? ▾
I also take warfarin for a blood clot — is it safe to take both? ▾
Can my child take this — and is it the same for kids as for adults? ▾
I'm 68 years old — is this medication safe for me? ▾
Is Zafirlukast available over the counter? ▾
When was Zafirlukast first available? ▾
Who makes Zafirlukast? ▾
💬 Answers drafted from Zafirlukast’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Zafirlukast comes
Zafirlukast is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Tablet
How this form is used
- Used for the long-term prevention and treatment of asthma in adults and children 5 years of age and older
- Helps reduce ongoing asthma symptoms by blocking leukotriene receptors in the airways
- Not intended to treat sudden (acute) asthma attacks — it is a maintenance therapy taken every day
- Take on an empty stomach — at least 1 hour before or 2 hours after a meal, as food reduces absorption by about 40%
- Taken twice daily; follow your prescriber's instructions for your specific dose
- Adults and children 12 and older, and children ages 5–11, each have their own dosing schedules — follow your prescription label exactly
- Do not stop taking zafirlukast during an asthma flare-up unless your doctor tells you to — therapy can continue during acute episodes
📊 Zafirlukast across the U.S. market
How Zafirlukast appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
Also listed with the FDA, not a patient dose form: Powder (6) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
📈 How widely Zafirlukast is used
A general measure of how commonly Zafirlukast is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Zafirlukast is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Zafirlukast prescribed? Of the 1,596 medications we measure, Zafirlukast ranks #984 by Medicaid prescriptions — more than 38% of them.
Utilization by Zafirlukast product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
zafirlukast 20 MG Oral Tablet Most dispensed
Summed across the 4 of 20 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 199655
zafirlukast 10 MG Oral Tablet
Summed across the 4 of 17 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 313758
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Zafirlukast, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 8 of 37 listed Zafirlukast NDCs with Medicaid activity.
🔍 Compare Zafirlukast products
A representative set of FDA-listed product records for Zafirlukast — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Tablet | ||||
| 20 mg | Oral | American Health Packaging × 2 listings | ANDA | View NDC → |
| 10 mg | — | Aurobindo Pharma Limited | DRUG FOR FURTHER PROCESSING | View NDC → |
| 10 mg | Oral | Aurobindo Pharma Limited | ANDA | View NDC → |
| 20 mg | Oral | Aurobindo Pharma Limited | ANDA | View NDC → |
| 20 mg | — | Aurobindo Pharma Limited | DRUG FOR FURTHER PROCESSING | View NDC → |
| 10 mg | Oral | AvKARE × 2 listings | NDA | View NDC → |
| 20 mg | Oral | AvKARE × 2 listings | NDA | View NDC → |
| 10 mg | Oral | Bryant Ranch Prepack × 2 listings | NDA | View NDC → |
| 20 mg | Oral | Bryant Ranch Prepack | ANDA | View NDC → |
| 10 mg | Oral | Camber Pharmaceuticals, Inc. | ANDA | View NDC → |
| 20 mg | Oral | Camber Pharmaceuticals, Inc. | ANDA | View NDC → |
| 10 mg | Oral | Dr. Reddys Laboratories Limited | ANDA | View NDC → |
| 20 mg | Oral | Dr. Reddys Laboratories Limited | ANDA | View NDC → |
| 10 mg | Oral | Par Pharmaceutical, Inc. × 2 listings | NDA | View NDC → |
| 20 mg | Oral | Par Pharmaceutical, Inc. × 2 listings | NDA | View NDC → |
| 10 mg | Oral | Rising Pharmaceuticals, Inc. | ANDA | View NDC → |
| 20 mg | Oral | Rising Pharmaceuticals, Inc. | ANDA | View NDC → |
| 10 mg | Oral | Strides Pharma Science Limited | NDA AUTHORIZED GENERIC | View NDC → |
| 10 mg | Oral | Strides Pharma Science Limited × 2 listings | NDA | View NDC → |
| 20 mg | Oral | Strides Pharma Science Limited | NDA AUTHORIZED GENERIC | View NDC → |
| 20 mg | Oral | Strides Pharma Science Limited × 2 listings | NDA | View NDC → |
| 💊Bulk drug substance | ||||
| 1 kg/kg | — | Chromo Laboratories India Private Limited × 2 listings | BULK INGREDIENT | View NDC → |
| 1 kg/kg | — | Dr.Reddy's Laboratories Limited | BULK INGREDIENT | View NDC → |
| 1 kg/kg | — | Hetero Drugs Limited | BULK INGREDIENT | View NDC → |
| 1 kg/kg | — | MSN Pharmachem Private Limited | BULK INGREDIENT | View NDC → |
| 30 kg/30 kg | — | Par Active Technologies Private Limited | BULK INGREDIENT | View NDC → |
Showing 35 of 35 products — FDA National Drug Code Directory. See every product, package size and price: browse all 35 Zafirlukast NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Zafirlukast — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Zafirlukast in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Zafirlukast went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 114970 1 dose form · 2 strengths
-
Dose form (SCDF) Oral Tablet RxCUI 374330In current FDA listings
Look up RxCUI 114970 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Zafirlukast is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Zafirlukast belongs to the Leukotriene Receptor Antagonist class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 7 FDA-filed SPL label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Strides Pharma Science Limited is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.