Fexofenadine

Fexofenadine is an over-the-counter second-generation antihistamine used in the treatment of various allergic symptoms. It is selective for the H receptor, carries little-to-no activity at off-targets, and does not cross the blood-brain barrier - this is in contrast to previous first-generation antihistamines, such as diphenhydramine, which readily bind to off-targets that contribute to side effects such as sedation. Fexofenadine is the major active metabolite of terfenadine and is administered as a racemic mixture in which both enantiomers display approximately equivalent antihistamine activity.

In the United States, fexofenadine is indicated for the symptomatic treatment of allergic rhinitis in patients ≥2 years old and chronic idiopathic urticaria in patients ≥6 months old. In Canada, fexofenadine carries the same indications but is approved only for patients ≥12 years old. Fexofenadine is also available in combination with pseudoephedrine for the symptomatic treatment of season allergic rhinitis in patients ≥12 years old.