Across 30 randomized trials and over 1,100 patients, cannabinoid medications outperformed conventional anti-nausea drugs for chemotherapy-induced vomiting, and patients overwhelmingly preferred cannabinoids.
Read this if you're undergoing chemotherapy and want to understand the evidence for cannabinoid anti-nausea medications.
NNT of 3.4: treat 3-4 patients with dronabinol for 1 additional to benefit vs. standard drugs
What the researchers found
This systematic review and meta-analysis examined 30 randomized clinical trials from over 12,000 initially identified papers, comparing cannabinoids to conventional anti-emetics and placebo for chemotherapy-induced nausea and vomiting.
Five meta-analyses were conducted. Dronabinol significantly outperformed neuroleptic anti-emetics (RR=0.67, NNT=3.4), meaning only 3-4 patients needed treatment with dronabinol instead of neuroleptics for one additional patient to benefit. Dronabinol versus placebo showed a trend favoring dronabinol (RR=0.47) but didn't reach significance.
Nabilone and levonantradol showed similar but non-significant trends against neuroleptics.
The most striking finding was patient preference: across 1,138 patients, the preference for cannabinoids over other drugs was overwhelming (RR=0.33, NNT=1.8), meaning nearly every other patient preferred the cannabinoid.
However, adverse effects were more frequent and intense with cannabinoids than conventional drugs.
Why it matters
This was one of the most comprehensive meta-analyses of cannabinoids for chemotherapy nausea at the time. The clear superiority over neuroleptic anti-emetics and overwhelming patient preference provided strong evidence for cannabinoids in this indication.
The numbers in context
30 RCTs from 12,749 papers. Dronabinol vs. neuroleptics: RR=0.67, NNT=3.4. Patient preference for cannabinoids: RR=0.33, NNT=1.8 (n=1,138). Adverse effects more common with cannabinoids.
How the study worked
Systematic review of PUBMED, EMBASE, PSYCINFO, LILACS, and Cochrane databases through December 2006. From 12,749 papers, 30 randomized clinical trials met inclusion criteria. Five meta-analyses were performed using relative risk and number needed to treat.
What this study cannot tell us
Many included trials were from the 1980s-1990s and used outdated comparator drugs (neuroleptics rather than modern anti-emetics like ondansetron). Some individual trials had small samples. The increased adverse effects of cannabinoids are clinically significant. Publication bias may favor positive results.
How to read the evidence
This is a systematic review and meta-analysis of 30 RCTs, the strongest form of evidence. However, the comparator drugs are largely outdated, limiting contemporary relevance.
When this study was published
Published in 2008. Modern anti-emetics (5-HT3 antagonists, NK1 antagonists) have changed the standard of care since many included trials were conducted. Cannabinoids are now typically used as adjunct or rescue therapy.
The bigger picture
This meta-analysis strengthened the evidence base for FDA-approved indications of dronabinol and nabilone for chemotherapy-induced nausea. However, it's worth noting that the comparator drugs (neuroleptics) are not the modern standard of care. Newer anti-emetics (5-HT3 antagonists like ondansetron) had already changed the landscape.
Questions still open
- How do cannabinoids compare to modern 5-HT3 antagonists like ondansetron? Could cannabinoids add benefit when used alongside modern anti-emetics? Does patient preference reflect true efficacy or the psychoactive effects?
Common questions
Are cannabinoids the best anti-nausea option for chemo?
Why do patients prefer cannabinoids despite more side effects?
Read the original research
Therapeutic use of Cannabis sativa on chemotherapy-induced nausea and vomiting among cancer patients: systematic review and meta-analysis.
European journal of cancer care, 17(5), 431-43
Citation
Machado Rocha, F C; Stéfano, S C; De Cássia Haiek, R; Rosa Oliveira, L M Q; Da Silveira, D X. (2008). Therapeutic use of Cannabis sativa on chemotherapy-induced nausea and vomiting among cancer patients: systematic review and meta-analysis.. European journal of cancer care, 17(5), 431-43. https://doi.org/10.1111/j.1365-2354.2008.00917.x
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