Newer non sedating antihistamines
Selective leukotriene receptor antagonist that inhibits the cysteinyl leukotriene (Cys LT 1) receptor.
Selectively prevents action of leukotrienes released by mast cells and eosinophils.
Effective first-generation agent but frequently produces sedation. Stimulate vasoconstriction by directly activating alpha-adrenergic receptors of the respiratory mucosa.
Only cetirizine causes drowsiness more frequently than placebo. Peak plasma levels reached within 1 h and half-life is about 8 h. Indicated for seasonal and perennial allergic rhinitis.
Competes with histamine for H1 receptors on GI tract, blood vessels, and respiratory tract, reducing hypersensitivity reactions. Pseudoephedrine stimulates vasoconstriction by directly activating alpha-adrenergic receptors of the respiratory mucosa.
Relieves nasal congestion and systemic effects of seasonal allergy.
For this reason, some second-generation antihistamines are available as combination preparations containing a decongestant.
They are often preferred for first-line therapy of allergic rhinitis, especially for seasonal or episodic symptoms, because of their excellent efficacy and safety profile. The second-generation oral antihistamines currently available in the United States are cetirizine, levocetirizine, desloratadine, fexofenadine, and loratadine.