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. Zafirlukast is marketed by Astra Zeneca with the brand names Accolate, Accoleit, and Vanticon. It was the first LTRA to be marketed in the USA and is now approved in over 60 countries, including the UK, Japan, Taiwan, Italy, Spain, Canada, Brazil, China and Turkey.