The purpose of this study is to evaluate the safety and effect of nasal carbon dioxide in the treatment of mild headaches in people who have migraines.

This multi-center, adaptively randomized, double-blind, placebo-controlled trial will evaluate the efficacy and safety of a nasal, non-inhaled administration of carbon dioxide (CO2) in the treatment of mild headaches. An estimated 250 patients who meet the eligibility criteria will be enrolled into this study at approximately 15 sites to ensure that about 220 patients are randomized and complete the study.

Inclusion Criteria:

• Able to read and understand informed consent form and voluntarily consent to participate in this study by signing the IRB-approved informed consent form
• Established diagnosis of migraine with or without aura per ICHD-II (patients with a diagnosis of only menstrual migraine are not eligible)
• History of 2-8 migraine attacks per month during the 3 months prior to randomization
• Have a typical migraine which progresses from a distinct mild headache to a moderate or severe migraine
• Able to recognize a mild headache that could develop into a moderate or severe migraine

Exclusion Criteria:

• Have less than 48 hours of freedom from headache between attacks of migraine
• Have 15 or more headache days per month
• Are females who are pregnant or lactating
• Use antipsychotic or antidepressant medications (unless only for migraine prophylaxis) within 12 weeks prior to randomization and for the duration of the study
• Have a concurrent diagnosis of TMD or trigeminal neuralgia requiring treatment
• Clinically significant deviated septum, nasal polyps or other nasal condition that prevents unrestricted breathing through each nostril
• Have participated in another study with nasal CO2