Montelukast Sodium is the orally bioavailable monosodium salt of montelukast, a selective cysteinyl leukotriene receptor antagonist with anti-inflammatory and bronchodilating activities. Montelukast selectively and competitively blocks the cysteinyl leukotriene 1 (CysLT1) receptor, preventing binding of the inflammatory mediator leukotriene D4 (LTD4). Inhibition of LTD4 activity results in inhibition of leukotriene-mediated inflammatory events including: migration of eosinophils and neutrophils; adhesion of leukocytes to vascular endothelium, monocyte and neutrophil aggregation; increased airway edema; increased capillary permeability; and bronchoconstriction.

Levocetirizine Dihydrochloride is the dihydrochloride salt form of the active levorotatory enantiomer of cetirizine, levocetirizine; a third generation, non-sedating, selective histamine H1 receptor antagonist, with antihistamine, anti-inflammatory and potential anti-angiogenic activities. Levocetirizine competes with endogenous histamine for binding at peripheral H1-receptor sites on the effector cell surface. This prevents the negative symptoms associated with histamine release and an allergic reaction. In addition, as histamine plays an important role in angiogenesis during an allergic inflammatory reaction, blocking the action of histamine may modulate the expression of proangiogenic factors and thus may prevent angiogenesis. As a third-generation histamine H1 receptor antagonist, levocetirizine has fewer side effects than most second-generation antihistamines.