LOW-DOSE CLEMASTINE INHIBITS SNEEZING AND RHINORRHEA DURING THE EARLYNASAL ALLERGIC REACTION

Background: Clemastine (1 mg) is currently available over-the-counter for the treatment of allergic rhinitis Objective: To evaluate the effi cacy of half the standard dose of clemastine (0.5 mg) in inhibiting th e nasal response to allergen and the cutaneous response to histamine. Methods: Double-blind, placebo-controlled, crossover study of 20 aller gic subjects out of season. The subjects received placebo or clemastin e administered one, four, and six hours before the challenges. Filter paper discs were used both to challenge the nasal mucosa with diluent and allergen and collect generated secretions. Sneezes, secretion weig hts, nasal and ocular symptoms, and albumin levels in nasal secretions were monitored for the nasal challenge. Intradermal skin testing was performed with diluent followed by histamine and the wheal and flare r eactions were measured, Results: There was a significant reduction in the number of sneezes after clemastine administered one, four, and six hours prior to challenge compared with placebo (P < .01). Clemastine administered four and six hours before challenge reduced sneezing sign ificantly more than clemastine administered one hour before challenge (P < .05). Antigen-induced increases in secretion weights and symptoms of rhinorrhea were significantly reduced compared with placebo only w hen clemastine was administered four and six hours prior to challenge (P < .05). Pretreatment with clemastine had no significant inhibitory effects on other nasal symptoms or on albumin levels in nasal secretio ns, an objective index of increased vascular permeability. Pretreatmen t with clemastine did not inhibit the histamine-induced wheal skin rea ction but showed a tendency, when administered six hours prior to the intradermal challenge, to reduce the flare reaction induced by the low est dose of histamine (P = .05), Conclusions: The data show that clema stine, given at half the usual dose four and six hours prior to allerg en challenge, provides relief for sneezing and rhinorrhea and suggests that this dose might be useful in the treatment of allergic rhinitis.