What does singulair (montelukast) do? can it break up mucus?

Treat Asthma/Allergy: Yes it can help with mucus. Singulair (montelukast sodium, msd), is a selective orally active leukotriene receptor antagonist that specifically inhibits the cysteinyl leukotriene cyslt1 receptor. In asthma, leukotriene-mediated effects include a number of airway actions, including bronchoconstriction, mucous secretion, vascular permeability, and eosinophil recruitment.