True about zafirlukast is :

Zafirlukast and montelukast are cysteinyl leukotriene receptor antagonists. They cause modest improvement in lung function and reduction in asthma symptoms and lessen the need for beta-agonist rescue therapy. These drugs can be considered as alternatives to low-dose inhaled corticosteroids in patients with persistent asthma. Zafirlukast is long-acting and can be given twice to once daily orally. It is a modest bronchodilator that reduces asthma morbidity, provides protection against exercise-induced asthma and diminishes nocturnal symptoms. These are less effective than corticosteroids.