Nasal Carbon Dioxide Used As Needed in the Symptomatic Treatment of Seasonal Allergic Rhinitis

Nasal, noninhaled carbon dioxide (CO2) was shown to be effective for the treatment of symptoms of seasonal allergic rhinitis (SAR) and perennial allergic rhinitis in single application studies. To assess the efficacy of as-needed treatment with nasal, noninhaled CO2 in patients with SAR. Fifty-six ragweed-allergic patients were enrolled at 3 sites in this study. After a 3- to 7-day run-in, 32 eligible patients who had an instantaneous total nasal symptom score of 8 or more out of a maximum of 12 in at least 2 SAR episodes per day were randomized to the CO2 group (n = 19) or to the placebo group (n = 13). A 10-second/nostril application was used as needed for 14 days (maximum 6 times/d). Patients evaluated their symptoms before and 30 minutes after each application. All symptoms were scored on a 0 to 3 scale. Analysis of all treated episodes (CO2 = 816, placebo = 516) showed a statistically significant beneficial change in total nasal symptom score from baseline (effect size = −0.51; P < .001). The effect size was larger with more severe baseline symptoms (baseline severities of ≥6 = −0.98; ≥8 = −1.14; and ≥10 = −1.61; all P < .001). CO2 was well tolerated, with transient nasal discomfort as the most common adverse event reported. There were no serious adverse events, serious adverse device effects, or early discontinuations. Nasal, noninhaled CO2 is effective for the as-needed treatment of SAR symptoms. The effect is rapid and the effect size is large. It represents a novel potential option for the as-needed treatment of rhinitis symptoms.