Objective: Nausea and vomiting is a common complaint of ED patients. Most previous studies of nausea and vomiting involve post-operative and oncology patients. The objective is to compare the efficacy of usual (4mg) and low (2mg) dose ondansetron and 10mg metoclopramide in relief of nausea and vomiting in ED patients. Methods: This is a prospective, randomized, double-blind study of adult ED patients with nausea and at least 1 episode of vomiting within 12 hours of presentation in a 65,000 visit ED teaching hospital. A validated 100mm visual analog nausea scale (VAS) was used prior to medication and 30 minutes post-treatment. Patients also rated their nausea post-treatment on a subjective scale. All patients received at least 500cc of saline IV. End points were complete relief of nausea, significant reduction of initial VAS, subjective change in nausea and adverse events. Analysis by ANOVA and Kruskal-Wallis. Results: 132 patients were enrolled over a 12 month period in 2005-2006. Initial VAS scores were similar with a mean of 66.4mm. All 3 groups had a significant and similar reduction in VAS with a mean final VAS score of 33.6 mm, p< 0.0001. There was no difference between the groups (power=0.87). 55.3% obtained >50% relief and 18.2% obtained complete relief, with no difference between groups. More nausea was experienced by 7.6% in the post-treatment odansetron groups and none in the metoclopramide group. None of the patients had an adverse reaction, 95% CI 0.0 – 2.2%. Conclusions: Low and usual dose odansetron and metoclopramide are efficacious in ED patients with nausea and vomiting without significant difference between the drugs. No adverse events occurred with either drug. Significant cost savings with similar efficacy would occur by using low-dose odansetron or metoclopramide in ED patients with nausea and vomiting. Reprinted with permission from Elsevier Inc. Acad Emerg Med 2007;14(Suppl):S16.