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), taken once daily. Zileuton (Zyflo), also used in the treatment of asthma via its inhibition of 5-lipoxygenase, is taken four times per day. Zafirlukast blocks the action of the cysteinyl leukotrienes on the CysLT1 receptors, thus reducing constriction of the airways, build-up of mucus in the lungs and inflammation of the breathing passages. Healthy young men who received a single oral 40 mg dose attained peak plasma zafirlukast concentrations that averaged 607 μg/L at 3.4 hours. The elimination half-life ranged from 12 to 20 hours.
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