Efficacy and safety of levocetirizine in seasonal allergic rhinitis.

OBJECTIVE: Pharmacodynamic studies have demonstrated that levocetirizine is the active enantiomer of cetirizine. This first therapeutic trial of levocetirizine aimed at determining the dosage with the best benefit/risk ratio in patients with seasonal allergic rhinitis (SAR). METHODS: Patients with seasonal allergic rhinitis were randomised in a placebo-controlled, double-blind, parallel-group multicentre study 2.5, 5, 10 mg levocetirizine or placebo once daily during 2 weeks. Patients filled in a diary evaluation card every evening before taking study medication using the classical (0-3) scale for assessment of severity of sneezing, rhinorrhea, nasal congestion, nasal pruritus and ocular pruritus over the preceding 24 hours. The Total Four-Symptom Score (T4SS) was calculated by adding the individual symptom scores, excluding nasal congestion. RESULTS: 470 patients were included and constituted the intent-to-treat population. All 3 doses of levocetirizine were significantly superior to placebo in reducing the mean T4SS over the 2 weeks (all P (0.001). Additionally, individual symptom severity scores for sneezing, rhinorrhea, itchy nose, and itchy eyes were also significantly decreased for all doses of levocetirizine. Levocetirizine was significantly superior to placebo in reducing symptom severity with an important global treatment effect (P = 0.0001), except for nasal congestion. Furthermore, there was simple linear relationship between levocetirizine dosages and reduction of T4SS (P = 0.001). All doses were well tolerated, somnolence was higher with 10 mg (10.2%) than 5 mg (1.7%) and other adverse events were more frequent with the highest dose. CONCLUSION: Levocetirizine 5 mg once daily has an optimal benefit/risk ratio in the treatment of SAR.