Which of the following drug is a leukotriene receptor antagonist?

Montelukast and zafirlukast inhibit the bronchoconstrictor action of LTs at cys LT1 receptor. These are used as prophylactic agents for bronchial asthma. These are very safe drugs but few cases of Churg Strauss syndrome (vasculitis with eosinophilia) have been associated with their use.