Classifications: bronchodilator (respiratory smooth muscle relaxant); leukotriene receptor antagonist;
Therapeutic: bronchodilator
; leukotriene receptor antagonist
Pregnancy Category: B


10 mg, 20 mg tablets


Selective leukotriene receptor antagonist (LTRA) that inhibits binding of leukotriene D4 and E4, thus inhibiting inflammation and bronchoconstriction. Leukotriene production and receptor affinity have been correlated with the pathogenesis of asthma.

Therapeutic Effect

Zafirlukast helps to prevent the signs and symptoms of asthma, including airway edema, smooth muscle constriction, and altered cellular activity due to inflammation.


Prophylaxis and chronic treatment of asthma in adults and children >5 y (not for acute bronchospasm).


Hypersensitivity to zafirlukast; acute asthma attacks, including status asthmaticus, acute bronchospasm; lactation, children <5 y.

Cautious Use

Hepatic impairment, hepatic disease; concurrent administration with warfarin; corticosteroid withdrawal or reduction in dose; patients ≥65 y, pregnancy (category B).

Route & Dosage

Adult: PO 20 mg b.i.d. 1 h before or 2 h after meals
Child (>5 y): PO 10 mg b.i.d.


  • Give 1 h before or 2 h after meals.
  • Store at 20°–25° C (68°–77° F); protect from light and moisture.

Adverse Effects (≥1%)

Body as a Whole: Generalized pain, asthenia, myalgia, fever, back pain. CNS: Headache, dizziness. GI: Nausea, diarrhea, abdominal pain, vomiting, dyspepsia; liver dysfunction, increased liver function tests, hepatic failure. Other: Churg-Strauss syndrome (fever, muscle aches and pains, weight loss).


Drug: May increase prothrombin time (PT) in patients on warfarin. Erythromycin decreases bioavailability of zafirlukast.


Absorption: Rapidly from GI tract, bioavailability significantly reduced by food. Onset: 1 wk. Peak: 3 h. Distribution: >99% protein bound; secreted into breast milk. Metabolism: In liver (CYP2C9). Elimination: 90% in feces, 10% in urine. Half-Life: 10 h.

Nursing Implications

Assessment & Drug Effects

  • Assess respiratory status and airway function regularly.
  • Lab tests: Periodic liver function tests.
  • Monitor closely PT and INR with concurrent warfarin therapy.
  • Monitor closely phenytoin level with concurrent phenytoin therapy.

Patient & Family Education

  • Taking medication regularly, even during symptom-free periods.
  • Note: Drug is not intended to treat acute episodes of asthma.
  • Report S&S of hepatic toxicity (see Appendix F) or flu-like symptoms to physician. Follow-up lab work is very important.
  • Notify physician immediately if condition worsens while using prescribed doses of all antiasthmatic medications.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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