MODE OF ACTION
Montelukast is a highly selective leukotriene receptor antagonist that binds with high affinity to the cysteinyl leukotriene receptor for leukotrienes D4 and E4. These leukotrienes are excreted by various types of cells, such as mast cells, and are involved the inflammatory process that may cause the signs and symptoms of asthma and allergic rhinitis. Leukotriene receptors are found in airway cells, such as macrophages and smooth muscle cells. When bound to leukotriene receptors, montelukast inhibits leukotriene physiologic effects without exhibiting any agonist activity.
Levocetirizine is a third generation, non-sedating, selective histamine H1 receptor antagonist, with antihistamine, anti- inflammatory and potential anti – antagonist activities. Levocetizine competes with endogenous histamine for binding at peripheral H1-receptor sites on the effectors cell surface. This prevents the negative symptoms associated with histamine release and an allergic reaction.