What is Zafirlukast?

It inhibits both early and late bronchoconstriction responses to inhaled antigens and stimulants. But it is not suitable for treating acute asthma attacks. This drug is used in the treatment of chronic asthma, which is administered orally in the amount of 20 mg, twice a day, which should be taken at least one hour before or 2 hours after a meal. For children 5 to 11 years old, a dose of 10 mg can be given twice a day.
Asthma is a common disease caused by inflammation of the airways. This inflammation causes irritation to the muscles around the airways. Therefore, the entry and exit of air into the lungs is difficult. This condition can cause symptoms such as wheezing, chest tightness and shortness of breath. This inflammation also causes the lining of the airways to produce more mucus.


Zafirlukast Mechanism of action

Zafirlukast is a selective antagonist for the 4D receptor leukotriene, a receptor stimulated by circulating leukotrienes plays an important role in the pathogenesis of asthma.


The pharmacokinetics of Zafirlukast

Peak plasma concentrations of zephyrlocast occur approximately 3 hours after oral administration. The absolute bioavailability rate is unknown, but administration with food reduces the rate and rate of absorption, resulting in a bioavailability rate of about 40%. Zephyrlocast is approximately 99% bound to plasma proteins and is extensively metabolized in the liver, especially by cytochrome 450p- and isoenzyme 9C2CYP. About 10% of the dose is excreted in the urine as fecal metabolites. Its half-life is about 10 hours. Animal studies suggest that small amounts of it cross the placenta and are distributed in low concentrations in breast milk.

Zafirlukast Side effects

Central nervous system: headache
Central nervous system: dizziness, pain
Gastrointestinal: nausea, diarrhea, abdominal pain, vomiting, indigestion
Hepatic: Increased serum levels of alanine aminotransferase
Infectious: Infection
Nervous, musculoskeletal: back pain, muscle aches, weakness
Miscellaneous: Fever

Zafirlukast Interactions

General specifications of interactions:

CYP2C9 inhibitor (weak)

Category X Interactions (Avoidance):


Reducing the effects of drugs by zephyrlocast:

No significant interference has been identified.

Reducing the effects of zephyrlocast by drugs:

Erythromycin (systemic), theophylline derivatives

Increased effects of drugs by zephyrlocast:

Fos phenytoin, phenytoin, loxapine, theophylline derivatives, tolbutamide, vitamin K antagonists

Enhancing the effects of zephyrlocast by drugs:

No significant interference has been identified.

Food interference:

  • Consumption with food reduces the bioavailability of the drug by up to 40%.
  • Solution: Take on an empty stomach (1 hour before or two hours after a meal).

Zafirlukast Warnings

This drug should not be used during asthma attacks because this drug has preventive effects and is ineffective during asthma attacks.
Tell your doctor if your asthma symptoms get worse
Smoking is prohibited in combination with this drug

Zafirlukast Prohibited usage

  • Pay attention to the expiration date of the medicine and do not take it if the medicine in your hand has expired.
  • Never give the medicine to anyone else, even if you have the same symptoms.
  • Do not take more than the dose prescribed by your doctor.
  • Check for drug interactions and be sure to tell your doctor what other medications you are taking.

Tips Before Consumption

Some medications can not be prescribed under certain conditions, and some medications may be prescribed if additional treatment is needed. Therefore, it is best for your doctor to be aware of the following before taking Zafirlukast:

• If you are pregnant or breast-feeding.
• If you have any liver or kidney problems.
• If you are currently taking certain medications. These medicines include all the medicines available, whether you are prescribed them or taking them without a doctor’s prescription, such as herbal medicines and complementary medicines.
• If you have ever been allergic to any medication.


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