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

Background

Noninhaled 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.

Objective

We studied whether noninhaled intranasal CO₂ would be effective in the treatment of seasonal allergic rhinitis.

Methods

We 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.

Results

Eighty-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.

Conclusion

Two 60-second intranasal CO₂ treatments resulted in rapid (10 minutes) and sustained (24 hours) relief of seasonal allergic rhinitis symptoms.

Key words: Carbon dioxide, topical nasal administration, clinical trial, allergic rhinitis

Abbreviations used: ANCOVA, Analysis of covariance, CGRP, Calcitonin gene-related peptide, TNNSS, Total non-nasal symptom score, TNSS, Total nasal symptom score