title: Improving SAR symptoms with levocetirizine: evaluating active and placebo effects in pollen challenge vs. natural exposure studies.
abstract: OBJECTIVE
  Despite a plethora of published data on levocetirizine, no meta-analyses exist on the effect of study design, and covariates like age, gender, and baseline symptom severity on treatment response. The objective of this study was the efficacy of levocetirizine 5  mg tablets and matching placebo at reducing allergy symptoms in adult subjects with seasonal allergic rhinitis under various pollen exposure study conditions and by age, gender and baseline symptom severity.
  
  
  METHODS
  This was a meta-analysis of original reports from randomized, double-blind, placebo-controlled studies. Clinical studies without detailed reports, open-label, non-randomized and non-controlled studies, or paediatric studies, were excluded. Study subjects were divided into an environmental exposure (EE) group or a natural exposure (NE) group.
  
  
  RESULTS
  Data from 3640 subjects were analysed (n = 2174 for levocetirizine, n = 1466 for placebo). The overall results confirmed the efficacy of levocetirizine 5  mg, with an approximately 40% symptom score improvement from baseline, in both the EE and NE groups. While levocetirizine showed no gender- or age-related differences in efficacy, female subjects responded better to placebo in the EE, but not in the NE group; younger subjects (<30 years of age) responded less favourably to placebo compared with older subjects (≥ 50 years of age). Levocetirizine was consistently superior to placebo regardless of baseline symptom score levels. The highest significance levels between the active and placebo groups were observed in subjects sensitized to animal dander and grass.
  
  
  CONCLUSIONS
  Differences between an oral antihistamine and placebo in clinical studies of allergic rhinitis might be due to a different response to placebo rather than to the active drug. Levocetirizine seems to have consistent efficacy regardless of age, gender, and baseline scores.
authors.affiliation: Global Medical Affairs Allergy, UCB Farchim SA, 10 Chemin de Croix Blanche, 1630 Bulle, Switzerland. rossen.boev@ucb.com
authors.forename: R
authors.initials: R
authors.lastname: Boev
authors.forename: D
authors.initials: D
authors.lastname: Song
authors.forename: A
authors.initials: A
authors.lastname: Bedenbaugh
authors.forename: J-M
authors.initials: JM
authors.lastname: Haeusler
mesh_terms: D000328:Adult; D000368:Aged; D001985:Bronchial Provocation Tests; D017332:Cetirizine / Q000009:adverse effects / Q000627:therapeutic use*; D004311:Double-Blind Method; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D039563:Histamine H1 Antagonists, Non-Sedating / Q000009:adverse effects / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D015990:Placebo Effect; D011058:Pollen / Q000009:adverse effects / Q000502:physiology; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D006255:Rhinitis, Allergic, Seasonal / Q000188:drug therapy*
chemical_list: D039563:Histamine H1 Antagonists, Non-Sedating; C472067:levocetirizine; D017332:Cetirizine