What is Montelukast? Montelukast (trade name Singulair) is a leukotriene receptor antagonist (LTRA) used for the maintenance treatment of asthma and to relieve symptoms of seasonal allergies. Montelukast comes as a tablet, a chewable tablet, flash tablet and granules to take by mouth. Montelukast may also be used for purposes not listed in this medication guide.