Intranasal noninhaled carbon dioxide for the symptomatic treatment of seasonal allergic rhinitis

BackgroundNoninhaled intranasal carbon dioxide (CO2) has been shown to be effective in the abortive treatment of migraine headache. Migraine headache is associated with trigeminal neuronal activation and release of calcitonin gene-related peptide, events also implicated in allergic rhinitis. Intranasal CO2 might inhibit trigeminal neuronal activation and suppress the release of calcitonin gene-related peptide.ObjectiveWe studied whether noninhaled intranasal CO2 would be effective in the treatment of seasonal allergic rhinitis.MethodsWe conducted a single-center, randomized, double-blind, placebo-controlled, parallel-group study. Treatment consisted of either CO2 (verum) or air (placebo) at a 2:1 ratio administered in each nostril for 60 seconds per nostril at a flow rate of 10 mL/s. The primary efficacy end point was the change from baseline in total nasal symptom score (TNSS), the sum of congestion, rhinorrhea, itching, and sneezing scored on a 0- to 5-point scale, at 30 minutes.ResultsEighty-nine subjects received treatment, 60 with CO2 and 29 with placebo, and all subjects completed the study. CO2 resulted in a statistically significant improvement in TNSS at 30 minutes over placebo (absolute changes of 5.0 for CO2 and 2.2 for placebo, P = .00019). Improvement from baseline in TNSS (CO2 vs placebo) was statistically significant at 10 minutes and remained so for 24 hours.ConclusionTwo 60-second intranasal CO2 treatments resulted in rapid (10 minutes) and sustained (24 hours) relief of seasonal allergic rhinitis symptoms.