Allegra has been approved as a treatment for seasonal allergic rhinitis. The labeling of Allegra recommends dosing of one 60-mg capsule, twice daily. The recommended starting dose for subjects with decreased kidney function is 60 mg, once daily. Allegra is available by prescription only.

The onset of action for Allegra was observed at one hour in a controlled clinical trial. Additional studies demonstrated that allergy sufferers continued feeling relief throughout the 12-hour dosing period. Also, two-week trials showed that Allegra provided significant symptom relief throughout the full course of therapy.

Clinical trials have demonstrated significant relief without sedating side effects. In clinical trials of more than 2,000 allergy sufferers, the incidence of adverse effects reported with Allegra was similar to placebo. Alegra studies have found no significant drug interactions with the macrolide antibiotic erythromycin and the antifungal ketoconazole. These agents have been known to interact with some other antihistamines. In addition, cardiac side effects reported were similar to placebo. The most commonly reported adverse experiences for Allegra and placebo are cold or flu (2.5% vs. 1.5%), nausea (1.6% vs. 1.5%), and menstrual pain (1.5% vs. 0.3%).