Nasal carbon dioxide for the symptomatic treatment of perennial allergic rhinitis

Background Brief nasal carbon dioxide insufflation has previously been shown to provide rapid relief of the symptoms of allergic rhinitis. Objective To examine the safety and efficacy of nasal carbon dioxide on the symptoms of perennial allergic rhinitis. Methods This was a randomized, double-blind, placebo-controlled, multicenter, in-clinic study that evaluated 2 flow rates (5 or 10 mL/s) and 2 administration durations (10 or 30 seconds per nostril) for nasal carbon dioxide vs placebo. Study participants rated their symptoms in clinic for 4 hours after administration and then through 24 hours outside the clinic. A total of 348 symptomatic patients with a minimum 2-year history of perennial allergic rhinitis requiring pharmacotherapy were randomized and treated. Results The mean change in total nasal symptom score from baseline at 30 minutes (the primary end point) showed greater improvement in the nasal carbon dioxide–treated groups compared with placebo. This change was statistically significant in the group treated with 10 mL/s for 10 seconds per nostril: −4.69 carbon dioxide vs −2.00 placebo ( P = .03). The effect of a single dose lasted approximately 4 to 6 hours. The mean change from baseline at 30 minutes in total nonnasal symptom score was also statistically significant (−4.06 carbon dioxide vs −2.25 placebo, P = .029) for this group. The most common adverse events were nasal discomfort, lacrimation, and headache. Conclusion The study provides further evidence that nasal carbon dioxide is a potentially efficacious treatment for the symptoms of allergic rhinitis.