ONSET OF ACTION AND EFFICACY OF TERFENADINE, ASTEMIZOLE, CETIRIZINE, AND LORATADINE FOR THE RELIEF OF SYMPTOMS OF ALLERGIC RHINITIS

Background: Terfenadine, astemizole, cetirizine, and loratadine are co mpared in their abilities to produce relief of symptoms of allergic rh initis. Objective: 111 ragweed-sensitive subjects were primed with pol len in the Environmental Exposure Unit. Study entry required adequate symptoms over a 3 hour exposure to 5000 +/- 300 grains/m(3) 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 a fter a 60-minute exposure. Allergen levels were maintained and symptom s recorded every 30 minutes. Results: Proportions of subjects with cli nically important relief were cetirizine, 69.6%; terfenadine, 54.5%; l oratadine, 50.0%; astemizole, 40.9%; and placebo, 31.8% but difference s weren't significant between treatment groups (P = .119). Survival cu rves for times to onset of clinically important relief for the four tr eatment groups were not different (P = .119). Subjects realizing defin itive relief were cetirizine, 65.2%; terfenadine, 45.5%; loratadine, 3 1.8%; placebo, 27.3%; and astemizole, 22.7% (P = .023). Survival analy sis 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 subje ct willingness to take the medication again yielded percentages: cetir izine, 82.6%; terfenadine, 66.7%; astemizole, 63.6%; loratadine, 40.9% ; and placebo, 36.4% (P = .036). Conclusion: Cetirizine and terfenadin e continuously ranked higher in terms of onset of action and efficacy, while loratadine and astemizole ranked lower. Significance was detect ed in definitive relief and relative efficacy.