 Numerous analogues have been organized; nonetheless, everyone of them resulted in diminishing antagonistic activity.Like montelukast, zafirlukast antagonizes bronchoconstrictive by selectively antagonising the CysLT1 receptor and affects all of the leukotrienes (LTC4, LTD4, and LTE4).The qualitative structural requirements and pharmacophore for CysLT1 antagonists were designed from the structural similarity of the agonist LTD4.