Fexofenadine, sold under the brand name Allegra among others,[10] is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.

[12] It does not cure, but rather prevents the aggravation of allergic rhinitis and chronic idiopathic urticaria, and reduces the severity of the symptoms associated with those conditions, providing relief from repeated sneezing, runny nose, itchy eyes or skin, and general body fatigue.

[20] Fexofenadine was also shown to inhibit histamine-induced wheal and flare to a significantly greater degree than loratadine or desloratadine,[21] but was slightly less effective than levocetirizine.

[23][24] The most common side effects include headache, back and muscle pain, miosis or pinpoint pupils, nausea, drowsiness, and menstrual cramps.

Fexofenadine was found to retain all of the biological activity of its parent while giving fewer adverse reactions in patients, so terfenadine was replaced in the market by its metabolite.

[29] Fexofenadine was originally synthesized in 1993 by Massachusetts-based biotechnology company Sepracor, which then sold the development rights to Hoechst Marion Roussel (now part of Sanofi-Aventis), and was later approved by the U.S. Food and Drug Administration (FDA) in 1996.

[citation needed] In January 2011, the FDA approved over-the-counter sales of fexofenadine in the United States, and Sanofi Aventis' version became available in March 2011.

[10] As of January 2017, it is marketed as a combination drug with pseudoephedrine under brand names including Alerfedine D, Allegra-D, Allergyna-D, Allevia, Altiva-D, Dellegra, Fexo Plus, Fexofed, Fixal Plus, Ridrinal D, Rinolast D, Telfast D, and Treathay.

[10] As of January 2017, it is marketed as a combination drug with montelukast under brand names including Fexokast, Histakind-M, Monten-FX, Montolife-FX, Montair-FX and Novamont-FX.