A triple-blind RCT of 33 cannabis users with active vomiting found haloperidol was significantly better than ondansetron at reducing pain and nausea, with shorter ED stays and less need for rescue medications.
Emergency physicians treating CHS, cannabis users who experience cyclic vomiting, and clinicians selecting first-line CHS treatments.
Haloperidol: 2.5 hours shorter ED stay
What the researchers found
Haloperidol was superior to ondansetron (difference 2.3 cm on VAS, 95% CI 0.6-4.0, p=0.01) with similar improvements in both pain and nausea. Haloperidol patients required fewer rescue antiemetics (31% vs 59%) and had shorter ED stays (3.1 vs 5.6 hours, difference 2.5 hours, p=0.03). Two patients in the higher-dose haloperidol group returned with acute dystonia.
Why it matters
This is one of the first RCTs comparing treatments for CHS. The superiority of haloperidol over ondansetron (a first-line antiemetic) confirms anecdotal reports and provides evidence to change emergency department practice for this increasingly common condition.
The numbers in context
33 enrolled, 30 treated; haloperidol vs ondansetron VAS difference: 2.3 cm (p=0.01); rescue antiemetics: 31% vs 59%; ED stay: 3.1 vs 5.6 hours (p=0.03); 2 dystonia events with high-dose haloperidol
How the study worked
Triple-blind randomized controlled trial. 33 cannabis users with active emesis randomized to haloperidol (with nested randomization to 0.05 or 0.1 mg/kg) or ondansetron 8 mg IV. Primary outcome: reduction in abdominal pain and nausea on 10-cm VAS at 2 hours.
What this study cannot tell us
Small sample (n=30 treated). Single-center study. Acute dystonia occurred with higher-dose haloperidol, raising safety concerns. Short-term outcomes only; no follow-up for recurrence.
How to read the evidence
Triple-blind RCT with objective outcomes, though small sample and single center.
When this study was published
Published in 2021; one of the first RCTs for CHS treatment.
The bigger picture
The efficacy of haloperidol (a dopamine antagonist) over ondansetron (a serotonin antagonist) provides insight into CHS pathophysiology, suggesting dopaminergic rather than serotonergic mechanisms underlie the vomiting. This has implications for understanding why traditional antiemetics fail in CHS.
Questions still open
- Is the lower haloperidol dose (0.05 mg/kg) sufficient and safer? How does haloperidol compare to other CHS treatments like capsaicin or benzodiazepines? Could a combination approach be more effective?
Common questions
What works best for cannabinoid hyperemesis syndrome?
Is haloperidol safe for CHS?
Read the original research
Intravenous Haloperidol Versus Ondansetron for Cannabis Hyperemesis Syndrome (HaVOC): A Randomized, Controlled Trial.
Annals of emergency medicine, 77(6), 613-619
Citation
Ruberto, Aaron J; Sivilotti, Marco L A; Forrester, Savannah; Hall, Andrew K; Crawford, Frances M; Day, Andrew G. (2021). Intravenous Haloperidol Versus Ondansetron for Cannabis Hyperemesis Syndrome (HaVOC): A Randomized, Controlled Trial.. Annals of emergency medicine, 77(6), 613-619. https://doi.org/10.1016/j.annemergmed.2020.08.021
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