Abstract: We included eight trials, involving 952 participants, of which 64% were women. Included trials were generally of adequate quality, with six trials at low risk of bias, and two trials at high risk of bias. Three trials with 518 participants compared five different drugs with placebo; all reported the primary outcome as mean change in visual analogue scale (VAS) (0 to 100) for nausea severity from baseline to 30 minutes. Trials did not routinely report other primary outcomes of the change in nausea VAS at 60 minutes or number of vomiting episodes. Differences in mean VAS change from baseline to 30 minutes between placebo and the drugs evaluated were: metoclopramide (three trials, 301 participants; mean difference (MD) -5.27, 95% confidence interval (CI) -11.33 to 0.80), ondansetron (two trials, 250 participants; MD -4.32, 95% CI -11.20 to 2.56), prochlorperazine (one trial, 50 participants; MD -1.80, 95% CI -14.40 to 10.80), promethazine (one trial, 82 participants; MD -8.47, 95% CI -19.79 to 2.85) and droperidol (one trial, 48 participants; MD -15.8, 95% CI -26.98 to -4.62). The only statistically significant change in baseline VAS to 30 minutes was for droperidol, in a single trial of 48 participants. No other drug was statistically significantly superior to placebo. Other included trials evaluated a drug compared to "active controls" (alternative antiemetic). There was no convincing evidence of superiority of any particular drug compared to active control. All trials included in this review reported adverse events, but they were variably reported precluding meaningful pooling of results. Adverse events were generally mild, there were no reported serious adverse events. Overall, the quality of the evidence was low, mainly because there were not enough data. In an ED population, there is no definite evidence to support the superiority of any one drug over any other drug, or the superiority of any drug over placebo. Participants receiving placebo often reported clinically significant improvement in nausea, implying general supportive treatment such as intravenous fluids may be sufficient for the majority of people. If a drug is considered necessary, choice of drug may be dictated by other considerations such as a person's preference, adverse-effect profile and cost. The review was limited by the paucity of clinical trials in this setting. Future research should include the use of placebo and consider focusing on specific diagnostic groups and controlling for factors such as intravenous fluid administered.

Plain-language summary: The evidence is current to August 2014. We included eight clinical trials of 952 participants. The trials assessed many different medicines at different doses, but only three trials included a placebo group (dummy medication). Six of these trials were of high quality, with low risk of error (i.e. bias, where the true effect is exaggerated). For this review, we included the effects of the medicines on nausea and vomiting up to one hour after the medicine was given. The main results of interest were the effect on nausea between zero and 60 minutes after the medicine was given, number of vomits and side effects to medicines. Of these, only nausea at 30 minutes and side effects were reported by all trials. From all trials, only one medicine was reported to be better than placebo and other medicines. That was droperidol, which was included in one small trial of 97 participants. No other single medicine was definitely better than any other medicine, and none of the other trials that included a placebo group showed that the active medicines definitely worked better than the placebo. Side effects were mild. Our results suggest that in people in the emergency department, nausea will generally improve, whether they are treated with specific medicines or placebo. Therefore, supportive treatment, such as intravenous fluids (where fluid is given directly into a blood vessel) may be sufficient for many people. Overall, the quality of the evidence was low, mainly because there was not enough data.