Zafirlukast (zafirlukast)

For the prevention and long-term symptomatic control of asthma, the usual dosage of zafirlukast for adults and children 12 years of age or older is 20 mg twice daily.

For the prevention and long-term symptomatic control of asthma, the usual dosage of zafirlukast for children 5-11 years of age is 10 mg twice daily.

Patients should be advised that zafirlukast must be taken at regular intervals to be therapeutically effective. In addition, patients should be advised that the drug will not provide immediate symptomatic relief and should not be used for the relief of acute bronchospasm; however, zafirlukast therapy generally should be continued during acute exacerbations of asthma. Patients should not discontinue or reduce the dosage of other antiasthmatic agents, even if they feel better as a result of initiation of zafirlukast therapy, unless instructed to do so by their clinician.

Although clearance of zafirlukast is reduced in geriatric patients 65 years of age or older (See Pharmacokinetics: Elimination), the overall incidence of adverse effects or study withdrawal because of adverse effects in clinical trials was comparable in geriatric or younger patients receiving zafirlukast 20 mg twice daily, and the manufacturer makes no specific recommendations regarding alteration of zafirlukast dosage solely on the basis of age.

Limited evidence in patients with stable alcoholic cirrhosis indicates that the peak plasma concentration and area under the plasma concentration-time curve (AUC) of zafirlukast are 50-60% higher in these patients relative to these pharmacokinetic values in patients with normal hepatic function. While the manufacturer currently makes no specific recommendations for adjustment of zafirlukast dosage in patients with hepatic impairment, the possibility that dosage reduction may be necessary should be considered. Zafirlukast has not been evaluated systematically in patients with hepatitis or in long-term studies in patients with cirrhosis.

Limited data suggest that renal impairment does not affect the pharmacokinetics of zafirlukast, and the manufacturer currently states that dosage adjustment in patients with renal impairment (e.g., creatinine clearance 10-30 mL/minute) is not necessary.

Zafirlukast is administered orally, usually in 2 equally divided doses daily. Because food generally decreases oral bioavailability of the drug, the manufacturer recommends that zafirlukast be taken on an empty stomach (i.e., at least 1 hour before or 2 hours after meals).

No dosing information is available for this tab.

No dosing information is available for this tab.

There is no enhanced messaging for this drug.

There are no contraindication interactions for this drug.

There are no severe interactions for this drug.

There are no moderate interactions for this drug.

There is no enhanced messaging for this drug.

There are no contraindication contraindications for this drug.

There are no severe contraindications for this drug.

There are no moderate contraindications for this drug.

There is no enhanced messaging for this drug.

There are no severe adverse reactions for this drug.

There are no less severe adverse reactions for this drug.

No enhanced messaging available.

No enhanced messaging available.

There are no adequate and well-controlled studies of zafirlukast in pregnant women. No evidence of teratogenicity was seen in reproductive studies in mice using oral dosages up to 1600 mg/kg daily (about 160 times the maximum recommended adult daily dosage on a mg/m2 basis), in rats using oral dosages up to 2000 mg/kg daily (about 410 times the maximum recommended adult daily dosage on a mg/m2 basis), and in cynomolgus monkeys using oral dosages up to 2000 mg/kg daily (about 20 times the maximum recommended adult daily dose based on AUC). In rats, administration of oral zafirlukast dosages of 2000 mg/kg daily resulted in maternal toxicity and deaths and an increased incidence of early fetal resorption. In cynomolgus monkeys, zafirlukast dosages of 2000 mg/kg daily resulted in maternal toxicity and spontaneous abortions.

The manufacturer states that zafirlukast should be used during pregnancy only when clearly needed. The American College of Obstetricians and Gynecologists (ACOG) and the American College of Allergy, Asthma, and Immunology (ACAAI) state that while leukotriene modifiers generally would not be used during pregnancy, use of zafirlukast or montelukast could be considered in patients with recalcitrant asthma who have shown a uniquely favorable response to the drugs prior to pregnancy.

Zafirlukast is distributed into milk. Following multiple-dose administration of zafirlukast 40 mg every 12 hours in healthy women, concurrent steady-state drug concentrations in breast milk or plasma averaged 50 or 255 ng/mL, respectively. Because of the potential for tumorigenicity associated with administration of zafirlukast in rodent studies and enhanced sensitivity of neonatal rats and dogs to adverse effects of the drug, zafirlukast should not be administered to women who are breast feeding.

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