C8. Medications: In addition to study medication or placebo, all subjects will receive standard migraine abortive therapy. The optimal migraine-abortive/analgesic medication for ED patients with acute migraine headaches has not yet been defined, so the investigators have chosen intravenous metoclopramide, an effective, safe, widely-available, and economical dopamine receptor antagonist, as the migraine treatment for this trial. Parenteral dopamine-antagonists are recommended for use in the ED29 and are used more commonly than triptans in the ED setting [1,16]. Metoclopramide has been shown to be at least as effective as subcutaneous sumatriptan at reducing pain [7,8] with comparable two hour activity limitations [30]. The investigators will use 20 milligrams of intravenous metoclopramide, a moderate dose when compared to their previous work [23,30]. In addition to metoclopramide, each subject will also receive 25mg of diphenhydramine to prevent akathisias and other extra-pyramidal reactions to the metoclopramide [31]. This combination of metoclopramide and diphenhydramine is commonly used in the ED setting and does not cause significant drowsiness or impairment of activities in migraineurs at two hours [30]. The investigators view the potential anti-migraine effect of diphenhydramine [32] as added benefit for their subjects. Metoclopramide, diphenhydramine, and the study medication will be placed into a 50cc bag of normal saline and administered as a slow intravenous drip over twenty minutes.