Zafirlukast; Uses, Dosage, Side Effects, Drug Interactions

Zafirlukast; Uses, Dosage, Side Effects, Drug Interactions

Zafirlukast is a tolyl compound and leukotriene receptor antagonist (LTRA), with anti-asthmatic and potential capsular contracture-preventing activities. Upon administration, zafirlukast selectively and competitively binds to and blocks the cysteinyl leukotriene 1 receptor (CYSLTR1), thereby preventing the potent pro-inflammatory mediator’s leukotriene C4, D4, and E4 from binding. This prevents leukotriene-mediated actions, including enhanced migration of eosinophils and neutrophils, increased adhesion of leukocytes, increased monocyte and neutrophil aggregation, increased airway edema, inflammation, capillary permeability, and bronchoconstriction. In addition, zafirlukast may decrease collagen deposition, fibrosis, and capsular thickness after implantation, thereby preventing scar tissue.

Zafirlukast is an orally administered leukotriene receptor antagonist (LTRA) used for the chronic treatment of asthma. While zafirlukast is generally well-tolerated, headache and stomach upset often occur. Zafirlukast is an oral leukotriene receptor antagonist (LTRA) for the maintenance treatment of asthma, often used in conjunction with an inhaled steroid and/or long-acting bronchodilator. It is available as a tablet and is usually dosed twice daily. Another leukotriene receptor antagonist is montelukast (Singulair), which is usually taken just once daily.

Mechanism of Action of zafirlukast

Zafirlukast is a selective and competitive receptor antagonist of leukotriene D4 and E4 (LTD4 and LTE4), components of slow-reacting substance of anaphylaxis (SRSA). Cysteinyl leukotriene production and receptor occupation have been correlated with the pathophysiology of asthma, including airway edema, smooth muscle constriction, and altered cellular activity associated with the inflammatory process, which contribute to the signs and symptoms of asthma. Patients with asthma were found in one study to be 25-100 times more sensitive to the bronchoconstricting activity of inhaled LTD4 than nonasthmatic subjects. In vitro studies demonstrated that zafirlukast antagonized the contractile activity of three leukotrienes (LTC4, LTD4, and LTE4) in conducting airway smooth muscle from laboratory animals and humans. Zafirlukast prevented intradermal LTD4-induced increases in cutaneous vascular permeability and inhibited the inhaled LTD4-induced influx of eosinophils into animal lungs.

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Indications of zafirlukast

Contra-Indications of zafirlukast

Dosages of zafirlukast

  • Strengths: 10 mg; 20 mg


  • 20 mg orally twice a day, 1 hour before or 2 hours after meals

Pediatric Asthma

Less than 5 years

  • The safety and effectiveness has not been established.

5 to 11 years

  • 10 mg orally twice a day, 1 hour before or 2 hours after meals

12 years or older

  • 20 mg orally twice a day, 1 hour before or 2 hours after meals

Maximum dosage

  • 40 mg/day PO.
  • 40 mg/day PO.
  • 40 mg/day PO.
  • 5—11 years: 20 mg/day PO.
  • < 5 years: Safety and efficacy have not been established.
  • Safety and efficacy have not been established.

Side Effects of zafirlukast

The most common


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Drug Interactions of zafirlukast

Zafirlukast may interact with following drugs, supplements & may change the efficacy of drugs

Pregnancy & Lactation of zafirlukast 

FDA pregnancy category B


This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

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Zafirlukast passes into breast milk. If you are a breastfeeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breastfeeding.





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