24-hour efficacy of once-daily desloratadine therapy in patients with seasonal allergic rhinitis [ISRCTN32042139]

Patients (N = 1,026) were randomly assigned once-daily (QD) desloratadine (2.5, 5, 7.5, 10, or 20 mg) for 2 weeks in a placebo-controlled, double-blind study. The end point of 24-hour efficacy was assessed by the mean change from baseline in the average AM instantaneous total symptom score (TSS) over the treatment period. Day 2 data were assessed for efficacy of desloratadine following the first dose. Other efficacy variables included AM/PM previous total nasal and nonnasal symptom scores and individual symptom scores.Desloratadine 5–20 mg was significantly (P < .01) more effective than placebo in improving total AM instantaneous TSS and AM/PM previous total nasal and nonnasal symptom scores. This dosing range also was significantly (P < .01) more effective than placebo for reducing AM instantaneous TSS beginning with the first dose; thus, demonstrating the full 24-hour efficacy of desloratadine. AM/PM previous scores for all individual symptoms, including nasal congestion, were also significantly improved versus placebo (P < .05) with desloratadine at 5, 7.5, and 20 mg. All treatments were well tolerated. There were no clinically meaningful changes in electrocardiogram parameters.Desloratadine 5–20 mg provided significant 24-hour relief of SAR signs and symptoms. There were no statistically significant differences between the 4 largest doses suggesting that desloratadine 5 mg QD offers the best therapeutic profile for patients with SAR.Second-generation oral antihistamines are among the most widely prescribed agents in the United States and Europe due to their effectiveness in the treatment of allergic diseases. Although newer long-acting antihistamine preparations permit once-daily dosing, many patients with seasonal allergic rhinitis (SAR) experience breakthrough symptoms and a diminution of clinical potency at the end of the dosing interval. Most antihistamines demonstrate a peak effect approximately 5 to 7 hours after oral administration, and the duration varie