Turns out, there’s truth inside those late-night infomercials and flashing banner ads on the Internet: the power to cure does, in fact, lie within ourselves. Or, possibly at least, decrease nausea.
This is a randomized, blinded, placebo-controlled trial comparing 4mg IV ondansetron vs. 20mg IV metoclopramide vs. saline solution placebo in Emergency Department patients with nausea & vomiting. 258 patients were evaluated, mostly evenly distributed between groups, and with similar causes of nausea. 30 minutes after administration, similar decreases in nausea were noted in each group, best visualized in this graph:
There were no differences in patient satisfaction with therapy, but fewer patients in the metoclopramide group required rescue therapy, and a greater number of placebo patients failed to have any symptom improvement (non-significant).
What lesson can be drawn from this? Uncertain. It is probably fair to say there is some placebo effect at work, and, considering there are centrally-acting mechanisms for nausea, they may in fact be curative. More likely, however, is that many of these causes of nausea & vomiting are simply self-limited, and resolve regardless of therapy. Further research might evaluate which specific causes resolve without therapy, and thus reduce costs and adverse effects associated with anti-emetic therapy.
“Antiemetic Use for Nausea and Vomiting in Adult Emergency Department Patients: Randomized Controlled Trial Comparing Ondansetron, Metoclopramide, and Placebo”
http://www.ncbi.nlm.nih.gov/pubmed/24818542
This isn't scientific, but I observe that many times , vomiting patients stop vomiting after being loaded with 500 mL Saline or Ringer.
Placebo maybe. Or not .
Actually, there's a couple other trials that used a 500mL bag of saline as the "placebo" arm – and it works to some extent, as well. There's a physiologic cascade of issues associated with dehydration and vomiting, and just restoring some of that intravascular volume seems to help.