What the label lists and what reports show
Zafirlukast side effects
Zafirlukast's FDA label lists its adverse reactions in its own words. FAERS holds 881 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is dyspnoea (108 reports).
- Generic listed
Check it at the source: the zafirlukast FDA label on DailyMed (effective December 1, 2023, Aurobindo Pharma Limited); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of zafirlukast tablets?Zafirlukast tablets may cause serious side effects, including: Severe liver problems. In some cases, these liver problems can lead to liver failure, the need for a liver transplant or death. Tell your healthcare provider right away if you have: pain or tenderness in the right upper side of your stomach area (abdomen) nausea tiredness itchiness yellowing of your skin or the whites of your eyes flu-like symptoms loss of appetite dark (tea colored) urine Inflammation of your blood vessels. Rarely, this can happen in people with asthma who take zafirlukast tablets. This usually, but not always, happens in people who also take a steroid medicine by mouth that is being stopped or the dose is being lowered. […]
Source: FDA drug label, Aurobindo Pharma Limited, effective December 1, 2023 (SPL set 8bdb47c5-9d19-4d59-94c8-62c117525e7f), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsAdults and Children 12 years of age and older The safety database for zafirlukast consists of more than 4000 healthy volunteers and patients who received zafirlukast, of which 1723 were asthmatics enrolled in trials of 13 weeks duration or longer. A total of 671 patients received zafirlukast for 1 year or longer. The majority of the patients were 18 years of age or older; however, 222 patients between the age of 12 and 18 years received zafirlukast. A comparison of adverse events reported by ≥1% of zafirlukast-treated patients, and at rates numerically greater than in placebo-treated patients, is shown for all trials in the table below. …
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
| Adverse Event | ZAFIRLUKAST N=4058 | PLACEBO N=2032 |
|---|---|---|
| Headache | 12.9% | 11.7% |
| Infection | 3.5% | 3.4% |
| Nausea | 3.1% | 2.0% |
| Diarrhea | 2.8% | 2.1% |
| Pain (generalized) | 1.9% | 1.7% |
| Asthenia | 1.8% | 1.6% |
| Abdominal Pain | 1.8% | 1.1% |
| Accidental Injury | 1.6% | 1.5% |
| Dizziness | 1.6% | 1.5% |
| Myalgia | 1.6% | 1.5% |
| Fever | 1.6% | 1.1% |
| Back Pain | 1.5% | 1.2% |
| Vomiting | 1.5% | 1.1% |
| SGPT Elevation | 1.5% | 1.1% |
| Dyspepsia | 1.3% | 1.2% |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
Source: FDA drug label, Aurobindo Pharma Limited, effective December 1, 2023 (SPL set 8bdb47c5-9d19-4d59-94c8-62c117525e7f), via openFDA; the full label on DailyMed
What do FAERS reports show?
881 reports list zafirlukast among the medicines taken, each a report of something that happened, not proof the medicine caused it; 43 are coded as a death and 210 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 21 reactions below, 11 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Zafirlukast: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions