A Study to Compare the Efficacy of Levocetirizine to Placebo in Reducing Symptoms of Seasonal Allergic Rhinitis (SAR) in Sensitive Subjects Exposed to Ragweed Pollen

Double Blind, Double-dummy, Five Parallel Groups, Randomized, Exploratory Clinical Trial to Compare the Efficacy of Single Dose of Levocetirizine 2.5 mg Oral Drops (5 mg/mL), Levocetirizine 5 mg Oral Tablets, Cetirizine 5 mg Oral Drops (10 mg/mL) and Cetirizine 10 mg Oral Tablets to Placebo in Reducing Symptoms of Seasonal Allergic Rhinitis (SAR) in Ragweed Sensitive Subjects Exposed to Ragweed Pollen in an Environmental Exposure Unit (EEU)

The purpose of the study is to assess the efficacy comparability of cetirizine and levocetirizine, by comparing the effects of single intake of the two drugs to placebo in reducing symptoms of seasonal allergic rhinitis (SAR) in ragweed sensitive adult subjects exposed to ragweed pollen in an Environmental Exposure Unit.

Inclusion Criteria:

• Female subject of non-childbearing potential or of childbearing potential agreeing not to become pregnant during the study.
• Have had seasonal allergic rhinitis due to Ragweed for the last 2 consecutive years
• Subjects who obtain a minimum sum considering SAR related symptoms (mean value) as defined by protocol

Exclusion Criteria:

• Any clinically significant condition that might interfere with the treatment evaluation, both for efficacy and safety
• Have used forbidden concomitant medications as defined by the protocol