Fexofenadine, the active metabolite of terfenadine, is a selective histamine H1 receptor antagonist that does not cross the blood brain barrier and appears to display some anti-inflammatory properties. Fexofenadine is rapidly absorbed (onset of relief < or = 2 hours) and has a long duration of action, making it suitable for once daily administration. Clinical trials (< or = 2 weeks' duration) have shown fexofenadine 60 mg twice daily and 120 mg once daily to be as effective as loratadine 10 mg once daily, and fexofenadine 120 mg once daily to be as effective as cetirizine 10 mg once daily in the overall reduction of symptoms of seasonal allergic rhinitis. When given in combination, fexofenadine and extended release pseudoephedrine had complementary activity. Fexofenadine was effective in relieving the symptoms of sneezing, rhinorrhoea, itchy nose palate or throat, and itchy, watery, red eyes in patients with seasonal allergic rhinitis. There were often small improvements in nasal congestion that were further improved by pseudoephedrine. Fexofenadine produced greater improvements in quality of life than loratadine to an extent considered to be clinically meaningful, and enhanced patients' quality of life when added to pseudoephedrine treatment. Although no comparative data with other H1 antagonists exist, fexofenadine 180 mg once daily was effective in reducing the symptoms of chronic idiopathic urticaria for up to 6 weeks. Fexofenadine was well tolerated in clinical trials in adults and adolescents and the adverse event profile was similar to placebo in all studies. The most frequently reported adverse event during fexofenadine treatment was headache, which occurred with a similar incidence to that seen in placebo recipients. Fexofenadine does not inhibit cardiac K+ channels and is not associated with prolongation of the corrected QT interval. When given alone or in combination with erythromycin or ketoconazole, it was not associated with any adverse cardiac events in clinical trials. As it does not cross the blood brain barrier, fexofenadine is free of the sedative effects associated with first generation antihistamines, even at dosages of up to 240 mg/day.
Conclusions: fexofenadine is clinically effective in the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria for which it is a suitable option for first-line therapy. Comparative data suggest that fexofenadine is as effective as loratadine or cetirizine in the treatment of seasonal allergic rhinitis. In those with excessive nasal congestion the combination of fexofenadine plus pseudoephedrine may be useful. In clinical trials fexofenadine is not associated with adverse cardiac or cognitive/psychomotor effects.