Study of levocetirizine in seasonal allergic rhinitis.

Objective: To evaluate the efficacy of levocetirizine 5 mg once daily in reducing seasonal allergic rhinitis (SAR) symptoms in US adults.

Research Design And Methods: This multicenter, randomized, double-blind, placebo-controlled, parallel-group study enrolled adults aged 18 to 65 years with SAR symptoms in the spring in the US. After a single-blind placebo run-in period, subjects received levocetirizine 5 mg or placebo once daily over 14 days. ClinicalTrials.gov registry no.: NCT00621959.

Main Outcome Measures: Primary efficacy variable was the Total 5-Symptom Score (T5SS). Secondary variables included Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ), Work Productivity and Activity Impairment-Allergy Specific (WPAI-AS) questionnaire, and Epworth Sleepiness Scale (ESS). Safety assessments were based on adverse events (AEs).

Results: The intent-to-treat population comprised 596 subjects (levocetirizine, n = 301; placebo, n = 295). Comparison of mean T5SS over the total treatment period showed a nonsignificant between-group difference (levocetirizine, 8.90 +/- 0.19; placebo, 9.04 +/- 0.19; adjusted mean difference, -0.14; p = 0.546). Levocetirizine showed numerical (mean RQLQ, WPAI-AS, ESS) and statistically superior differences (two domains within WPAI-AS) compared with placebo upon analysis of secondary efficacy variables. The incidence of treatment-emergent AEs was similar (levocetirizine, 23.9%; placebo, 24.4%). As the lack of efficacy was inconsistent with all previous levocetirizine studies, post hoc analyses were performed to assess the influence of pollen counts, geography, and other factors; however, no conclusive explanation could be identified.

Conclusions: In this study, levocetirizine 5 mg QD was well tolerated but failed to show significant efficacy compared with placebo in a US adult population with SAR. This finding is inconsistent with all previous studies with levocetirizine and in contrast to a concurrently run, similarly designed US study. It reflects the importance of conducting duplicate studies as there is always a small but real risk of false negative results in clinical studies, irrespective of the methodologic quality.