Histamine challenge and anterior nasal rhinometry: their use in the assessment of pseudoephedrine and triprolidine as nasal decongestants in subjects with hayfever.

1 Nasal airway resistance (NAR) was measured by anterior rhinometry in ten volunteers with allergic rhinitis. Measurements before and after challenge with three concentrations of histamine diphosphate showed significant rises in NAR for each challenge. 2 In a double-blind, crossover study with the same patients triprolidine (2.5 mg) and pseudoephedrine (60 mg) were shown to be equally effective in reducing the rise in NAR produced by histamine challenge to one nostril; both were significantly better than placebo. 3 The rise in NAR of both nostrils after histamine challenge to one nostril was significantly reduced after pseudoephedrine compared with placebo. This suggests that pseudoephedrine is effective in preventing reflex mucosal congestion in the unchallenged nostril. 4 No increase in the pulse rate or blood pressure of the volunteers was detected after either drug.