title: Onset of action and efficacy of terfenadine, astemizole, cetirizine, and loratadine for the relief of symptoms of allergic rhinitis.
abstract: BACKGROUND
  Terfenadine, astemizole, cetirizine, and loratadine are compared in their abilities to produce relief of symptoms of allergic rhinitis.
  
  
  OBJECTIVE
  The aim of this study was to compare the onset of action and efficacy of the study medications.
  
  
  METHODS
  111 ragweed-sensitive subjects were primed with pollen in the Environmental Exposure Unit. Study entry required adequate symptoms over a 3 hour exposure to 5000 +/- 300 grains/m3 of ragweed pollen. On the test day, subjects were given a single dose of either terfenadine 60 mg (22), astemizole 10 mg (22), cetirizine 10 mg (23), loratadine 10 mg (22), or placebo (22) when sufficiently symptomatic after a 60-minute exposure. Allergen levels were maintained and symptoms recorded every 30 minutes.
  
  
  RESULTS
  Proportions of subjects with clinically important relief were cetirizine, 69.6%; terfenadine, 54.5%; loratadine, 50.0%; astemizole, 40.9%; and placebo, 31.8% but differences weren't significant between treatment groups (P = .119). Survival curves for times to onset of clinically important relief for the four treatment groups were not different (P = .119). Subjects realizing definitive relief were cetirizine, 65.2%; terfenadine, 45.5%; loratadine, 31.8%; placebo, 27.3%; and astemizole, 22.7% (P = .023). Survival analysis of onset time for definitive relief found significant differences (P = .010). The ranking was cetirizine --> terfenadine --> loratadine --> astemizole (quickest to slowest). Global evaluation based on subject willingness to take the medication again yielded percentages: cetirizine, 82.6%; terfenadine, 66.7%; astemizole, 63.6%; loratadine, 40.9%; and placebo, 36.4% (P = .036).
  
  
  CONCLUSIONS
  Cetirizine and terfenadine continuously ranked higher in terms of onset of action and efficacy, while loratadine and astemizole ranked lower. Significance was detected in definitive relief and relative efficacy.
authors.affiliation: Division of Allergy and Immunology, Kingston General Hospital, Ontario, Canada.
authors.forename: J H
authors.initials: JH
authors.lastname: Day
authors.forename: M P
authors.initials: MP
authors.lastname: Briscoe
authors.forename: R H
authors.initials: RH
authors.lastname: Clark
authors.forename: A K
authors.initials: AK
authors.lastname: Ellis
authors.forename: P
authors.initials: P
authors.lastname: Gervais
mesh_terms: D000293:Adolescent; D000328:Adult; D018926:Anti-Allergic Agents / Q000627:therapeutic use*; D016589:Astemizole / Q000627:therapeutic use*; D017332:Cetirizine / Q000627:therapeutic use*; D004311:Double-Blind Method; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D017336:Loratadine / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011537:Pruritus / Q000517:prevention & control; D012221:Rhinitis, Allergic, Perennial / Q000188:drug therapy*; D006255:Rhinitis, Allergic, Seasonal / Q000188:drug therapy*; D012912:Sneezing / Q000187:drug effects; D016593:Terfenadine / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D018926:Anti-Allergic Agents; D017336:Loratadine; D016593:Terfenadine; D016589:Astemizole; D017332:Cetirizine