Vifas Mechanism of Action

Pharmacology: Pharmacodynamics: Fexofenadine, a second-generation antihistamine, is the active metabolite of terfenadine. Fexofenadine is a specific, selective, histamine H₁-receptor antagonist. Unlike terfenadine, Fexofenadine does not block the potassium channel involved in repolarization of cardiac cells. Fexofenadine also does not possess appreciable anticholinergic, antidopaminergic, or α- or β-adrenergic blocking effects at usual antihistaminic doses. Fexofenadine does not cross the blood-brain barrier at usual doses therefore the incidence of CNS effects or sedative effect are less than those of other antihistamines.
Pharmacokinetics: Fexofenadine is rapidly absorbed from the GI tract following oral administration, peak plasma concentrations are achieved in about 2.6 hours. Fexofenadine distributes more extensively into plasma than into blood or saliva. The drug does not appear to cross the blood-brain barrier. It is not known if Fexofenadine cross the placenta or is distributed into breast milk. Fexofenadine is 60-70% bound to plasma proteins, principally albumin and α1-acid glycoprotein. About 5% of a single oral dose of Fexofenadine is metabolized. Negligible amount are metabolized in the liver by the cytochrome P-450 microsomal enzyme system. About 80% of Fexofenadine is principally eliminated in feces and 11-12% is excreted in urine.