A randomized trial of dexamethasone 10 mg IV in 205 adult patients presenting with acute migraine to an emergency department (ED) found 25% of those with acute migraine became pain-free for at least 24 hours compared to 19% of those given placebo (p=0.34). Patients with status migrainosus (migraine lasting longer than 72 hours) received persistent relief in 38% compared to 13% following placebo (p=0.06). All patients also received IV metoclopramide and diphenhydramine as pimary treatment for migraine. Researchers from the Department of Emergency Medicine (ED), Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, advise that IV dexamethasone should not be administered routinely in ED treatment of acute migraine, but it might be considered for patients with migraine lasting longer than 72 hours. 
COMMENT. The authors comment that the benefit in persistent migraine relief rates found for dexamethasone in this study should be interpreted with caution because this was a subgroup analysis. Becker WJ, Kryscio RJ, in an editorial , note that others have reported benefits of dexamethasone, especially with larger doses and with headache endpoints beyond 24 hours post-treatment.