Pharmacologic prophylaxis of allergic rhinitis: relative efficacy of hydroxyzine and chlorpheniramine.

The efficacy of hydroxyzine and chlorpheniramine in preventing exacerbations of ragweed allergic rhinitis was compared in a double-blind, randomized manner. Ninety-five subjects with positive skin tests, a history of two previous symptomatic seasons, and discontinuation of immunotherapy for at least 1 yr received either hydroxyzine 150 mg/day, chlorpheniramine 24 mg/day, or placebo during the 1978 ragweed season. Subjects in the placebo group experienced annoying or disabling sneezing 50% of days during the period of highest pollen counts whereas those in the chlorpheniramine and hydroxyzine groups experienced this symptom with equal severity only 22% and 12% of days, respectively. Suppression of rhinorrhea and itchy nose was similar although less dramatic. Both antihistamines were more effective than placebo in altering conjunctivitis, but neither decreased the frequency or severity of nasal stuffiness. Skin tests to ragweed decreased in diameter during the season by 38%, 13%, and 3% among patients receiving hydroxyzine, chlorpheniramine, and placebo, respectively. Frequent drowsiness occurred initially in subjects taking both antihistamines but did not persist. Thus, prophylactic antihistamine therapy effectively prevents most symptoms of seasonal allergic rhinitis without persistent drowsiness. These data further suggest a therapeutic advantage for hydroxyzine over chlorpheniramine in the doses used.