Zafirlukast Side Effects

Medically reviewed by Drugs.com. Last updated on Mar 17, 2025.

Applies to zafirlukast: oral tablet.

Precautions

It is very important that your doctor check the progress of you or your child at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

You or your child may be taking other medicines for asthma along with zafirlukast. Do not stop taking or reduce the dose of the other medicines, even if your asthma seems better, unless you are told to do so by your doctor.

Check with your doctor if your or your child's symptoms do not improve or if your asthma gets worse.

Stop using this medicine and check with your doctor right away if you or your child have pain or tenderness in the upper stomach; pale stools; dark urine; loss of appetite; nausea; unusual tiredness or weakness; or yellow eyes or skin. These could be symptoms of a serious liver problem.

This medicine may cause a rare blood condition called Churg-Strauss syndrome. This usually occurs in patients who have asthma or are taking oral steroid medicines that is being stopped or the dose is being reduced or lowered. Tell your doctor right away if you or your child have the following symptoms: a feeling of pins and needles, flu-like symptoms, numbness of the arms or legs, rash, or pain and swelling of the sinuses.

This medicine may cause some people to be agitated, disoriented, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed and have problems with sleep. If you, your child, or your caregiver notice any of these side effects, tell your doctor or your child's doctor right away.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of zafirlukast

Along with its needed effects, zafirlukast may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking zafirlukast:

Other side effects of zafirlukast

Some side effects of zafirlukast may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

For healthcare professionals

Applies to zafirlukast: oral tablet.

General adverse events

The most commons adverse effects may be associated with headache or gastrointestinal disturbances. These symptoms are usually mild.^[Ref]

Nervous system

• Very common (10% or more): Headache (up to 12.9%)
• Common (1% to 10%): Dizziness (1.6%)
• Frequency not reported: Neuropathy, neuropsychiatric events^[Ref]

Gastrointestinal

• Common (1% to 10%): Nausea (up to 3.1%), diarrhea (up to 2.8%), abdominal pain (up to 2.8%), vomiting (up to 1.5%), dyspepsia (1.3%)^[Ref]

Hepatic

• Common (1% to 10%): SGPT elevation (1.5%), AST (1.4%)
• Rare (less than 0.1%): Hyperbilirubinemia without other elevated liver function tests; fulminant hepatitis or progressed to hepatic failure, liver transplantation and death
• Postmarketing reports: Symptomatic hepatitis (with or without hyperbilirubinemia) without other attributable cause; hepatic dysfunction^[Ref]

In most of the postmarketing reports, the patient's symptoms abated and the liver enzymes returned to normal or near normal after stopping this drug.^[Ref]

Musculoskeletal

• Common (1% to 10%): Myalgia (1.6%), back pain (1.5%)
• Frequency not reported: Arthralgia^[Ref]

Other

• Common (1% to 10%): Generalized pain (1.9%), asthenia (up to 1.8%), accidental injury (1.6%), fever (1.4%)
• Rare (less than 0.1%): Increased theophylline levels with or without clinical signs or symptoms of theophylline toxicity when this drug was added to an existing theophylline regime.
• Frequency not reported: Edema, malaise^[Ref]

Respiratory

• Common (1% to 10%): Respiratory tract infection (3.5%)^[Ref]

Infections were usually mild or moderate, predominantly affecting the respiratory tract and not necessitating withdrawal from the therapy.

In clinical trials, an increased proportion of patients over the age of 55 years reported these infections. Infections occurred equally in both sexes and were associated with coadministration of inhaled corticosteroids.^[Ref]

Cardiovascular

• Rare (less than 0.1%): Bleeding disorders including menorrhagia, thrombocytopenia^[Ref]

Dermatologic

• Rare (less than 0.1%): Alopecia
• Frequency not reported: Bruising, pruritus^[Ref]

Hematologic

• Rare (0.01% to 0.1%): Granulomatosis
• Very rare (less than 0.01%): Agranulocytosis^[Ref]

Immunologic

• Rare (less than 0.1%): Systemic eosinophilia, eosinophilic pneumonia, or clinical features of vasculitis consistent with Churg-Strauss syndrome^[Ref]

Systemic eosinophilia may also involve various body systems including vasculitic rash, worsening pulmonary symptoms, cardiac complications or neuropathy.^[Ref]

Hypersensitivity

• Frequency not reported: Urticaria, angioedema, rashes (with or without blistering)^[Ref]

Psychiatric

• Frequency not reported: Insomnia, depression^[Ref]

See also:

Further information

Zafirlukast side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer