Cetirizine (Zyrtec) may provide greater symptom relief than fexofenadine (Allegra) in patients who suffer from seasonal allergic rhinitis and documented ragweed sensitivity, according to a new Canadian study presented at the meeting of the American College of Allergy, Asthma & Immunology.
Results showed that average symptom relief was 26% better with 10 mg of cetirizine than with 180 mg of fexofenadine at 12 hours postdosing. However, average symptom relief from 5 to 12 hours after dosing, during the entire study period, was pegged at just 14% more in the cetirizine-treated patients compared with those receiving fexofenadine. Also, the difference in allergy relief was significantly greater with cetirizine compared with fexofenadine at 11 of the 15 time points measured.
These results are consistent with findings of a similar environmental exposure unit study published in Allergy and Asthma Proceedings (2004;1:59-68) showing a 33% better symptom relief for cetirizine-treated patients compared with those receiving fexofenadine at 21 to 24 hours after dosing.
“The data presented, coupled with the results of the previous study, provide clinicians with a more complete picture of how these 2 products will perform over the 24-hour dosing period,” said lead investigator James Day, MD, head of the Division of Allergy and Immunology, Kingston General Hospital, Ontario.
This randomized, double-blind, placebo-controlled, parallel group study included 599 patients (aged ³16 years) who had suffered from seasonal allergic rhinitis to ragweed pollen for the past 2 consecutive allergy seasons. Only patients with documented seasonal allergy to ragweed pollen as confirmed by a recognized skin test within the previous 15 months were included. Patients were randomly assigned to receive cetirizine (n = 249), fexofenadine (n =249), or placebo (n = 100).
All the patients were exposed to ragweed pollen in an environmental exposure unit, which was designed to actively mange levels of the allergen to ensure controlled contact. This assured that pollen levels comparable with concentrations observed during peak ragweed season would be consistently maintained and the course of exposure monitored to determine any symptomatic variability during the exposure period.
Patients’ symptoms were assessed using the total symptom severity complex (TSSC) score, defined as the sum of self-assessed severity scores for 4 rhinoconjunctivitis symptoms (ie, runny nose, sneezing, itchy nose/palate/throat, and itchy/watery eyes).
For total symptom improvement at 12 hours—the primary efficacy end point—patients treated with cetirizine had 26% greater relief than those who received fexofenadine. Cetirizine also scored better than fexofenadine on all 4 TSSC scores at 12 hours. Both agents were well tolerated, with low discontinuation rates because of treatment-related adverse events.