Zyrtec (cetirizine HCl 10 mg) provides on average 14 per cent greater symptom relief than Allegra (fexofenadine 180 mg) during the entire period of five to 12 hours after dosing in patients who suffer from seasonal allergic rhinitis and documented ragweed sensitivity, according to the new data presented at the 62nd annual meeting of the American College of Allergy, Asthma and Immunology.

In addition, the study results show, at the end of the 12-hour dosing period, Zyrtec patients reported even greater total relief as compared to Allegra patients. The difference in efficacy achieved statistical significance at 5.5 hours, and Zyrtec provided statistically significant allergy relief compared to Allegra at 11 of the 15 time points measured. The study was funded by Pfizer Inc.

These results are consistent with the findings of a similar environmental exposure unit (EEU) study published earlier this year in Allergy and Asthma Proceedings that showed 33 per cent greater symptom relief for Zyrtec patients compared with Allegra patients at 21-24 hours after dosing. "The data presented coupled with the results of the previous study provides the clinician with a more complete picture of how these two products will perform over the 24-hour dosing period," said James H. Day, study's principal investigator and head, Division of Allergy and Immunology, Kingston General Hospital, Kingston, Ontario.

The results showed that for total symptom improvement at 12 hours, the primary efficacy endpoint, patients treated with Zyrtec had 26 per cent greater relief than those who received Allegra; overall relief during the entire period from five to 12 hours following dosing was 14 per cent greater in Zyrtec-treated patients than in those treated with Allegra; patients in the Zyrtec group had greater reductions in TSSC scores than those in the Allegra group at all time points from five through 12 hours post-dose.

Both Zyrtec and Allegra were well tolerated with low levels of discontinuation because of treatment-related adverse events.

The primary objective of the study was to compare the relative efficacy of cetirizine HCl 10 mg daily, fexofenadine HCl 180 mg daily, and placebo in controlling the symptoms of seasonal allergic rhinitis at 12 hours post dose. The study involved 599 subjects 16 years of age and older who suffered from seasonal allergic rhinitis to ragweed pollen for the last two consecutive allergy seasons. Specifically, subjects with documented seasonal allergy to ragweed pollen as confirmed by a recognized skin test within the previous 15 months were qualified for the study.