EVALUATION OF A BEDTIME DOSE OF A COMBINATION ANTIHISTAMINE ANALGESICDECONGESTANT PRODUCT ON ANTIGEN CHALLENGE THE NEXT MORNING

The effects of CAAD (diphenhydramine hydrochloride, 50 mg; pseudoephed rine hydrochloride, 60 mg; acetaminophen, 1 g in 10% ethanol) were eva luated in a double-blind, three-way, placebo-controlled, cross-over st udy on 18 volunteers with allergic rhinitis. The number of sneezes fol lowing nasal challenge with antigen was significantly reduced after a bedtime dose of CAAD (P < .005) and a single dose of diphenhydramine ( P < .001) given 2 hours before the challenge. The levels of N-alpha-to syl-L-arginine methyl ester (TAME) activity decreased after diphenhydr amine treatment, while histamine levels following challenge were not d ifferent. The drowsiness reported after CAAD was equal to placebo, but significantly less than diphenhydramine (P < .002 for both). The acti ve treatments reduced the actions of histamine without suppressing its release from mast cells. The effect of CAAD persists 10 hours after a dministration without inducing drowsiness.