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 BRAND NAMES
 MECHANISM OF ACTION
Zafirlukast is an oral leukotriene receptor antagonist (LTRA)
Leukotrienes are a family of eicosanoid inflammatory mediators of asthma. They are generated from arachidonic acid as a result of the 5-lipoxygenase action in multiple inflammatory cells, particularly mast cells, basophils, eosinophils, neutrophils and macrophages and are responsible for the contraction of smooth muscle (bronchospasm), the increase in bronchial reactivity (mucus secretion), in vascular permeability and in eosinophil recruitment in asthmatics.
Zafirlukast acts as an antagonist of the cysteinyl-leukotriene-receptor CysLT1, and then is able to attenuate the bronchoconstriction.
Prophylaxis and chronic treatment of asthma. Zafirlukast is not indicated for use in acute asthma attacks.
- Adult and children 12 years of age and older: 20 mg twice daily, 1 hour before or 2 hours after meals.
- Pediatric patients 5-11 years: 10 mg twice daily, 1 hour before or 2 hours after meals.
- Hypersensitivity to zafirlukast
- Patients with hepatic impairment including hepatic cirrhosis
 WARNINGS AND PRECAUTIONS
- Cases of life-threatening hepatic failure have been reported rarely in patients treated with Zafirlukast. Patients should be advised to be alert for signs and symptoms of liver dysfunction (eg, right upper quadrant abdominal pain, nausea, fatigue, lethargy, pruritus, jaundice, flu-like symptoms, and anorexia) and if liver dysfunction is suspected, Zafirlukast should be discontinued.
- Eosinophilic Conditions: In rare cases, patients on Zafirlukast therapy may present with systemic eosinophilia, eosinophilic pneumonia, or clinical features of vasculitis consistent with Churg-Strauss syndrome, a condition which is often treated with systemic steroid therapy. These events usually, but not always, have been associated with the reduction of oral steroid therapy. It is, therefore, recommended that zafirlukast-treated patients who require a reduction in their oral corticosteroid therapy are closely monitored.
- Neuropsychiatric events have been reported in adult, adolescent, and pediatric patients taking Zafirlukast. Post-marketing reports with Zafirlukast use include insomnia and depression. The clinical details of some post-marketing reports involving Zafirlukast appear consistent with a drug-induced effect.
- Warfarin: Coadministration of zafirlukast with warfarin results in a clinically significant increase in prothrombin time (PT). Prothrombin times should be monitored closely and anticoagulant dose adjusted accordingly.
 PREGNANCY AND LACTATION
- Pregnancy Category B (US). Zafirlukast should be used during pregnancy only if clearly needed.
- Nursing Mothers: Zafirlukast is excreted in breast milk, therefore, it should not be administered to mothers who are breast-feeding.
 SIDE EFFECTS
Possible adverse effects include:
- CNS: Headache and dizziness
- GI: Nausea, diarrhea, abdominal pain, vomiting, liver enzyme elevation
- Other: Generalized pain, Asthenia, accidental injury and infection
- Rare but life-threatening:
- Churg-Strauss syndrome (eosinophilia, vasculitic rash, pulmonary and cardiac complications) when oral steroid dose is reduced.
- Hepatitis or liver failure