How Well Do Cannabinoids Control Chemotherapy Nausea? A Systematic Review of 30 Trials | Research

The takeaway

A systematic review of 30 trials found cannabinoids were more effective than conventional antiemetics for chemotherapy-induced nausea and vomiting, but caused significant side effects including dizziness, dysphoria, and hallucinations.

Read this if you or someone you know is dealing with chemotherapy-related nausea and considering cannabinoid medications.

NNT 6 for nausea control; NNT 8 for vomiting control across 1,366 patients

What the researchers found

Across 30 randomized trials with 1,366 patients, cannabinoids (nabilone, dronabinol, and levonantradol) outperformed conventional antiemetics for chemotherapy-induced sickness. For complete nausea control, the number needed to treat was 6; for complete vomiting control, it was 8. In crossover trials, patients preferred cannabinoids for future cycles by a wide margin (NNT 3 for preference).

However, cannabinoids also produced significantly more side effects. Dizziness occurred frequently (NNT 3), along with dysphoria or depression (NNT 8), hallucinations (NNT 17), paranoia (NNT 20), and low blood pressure (NNT 7). Some side effects were considered potentially beneficial, including feeling "high" (NNT 3), sedation (NNT 5), and euphoria (NNT 7). Patients on cannabinoids were more likely to withdraw due to side effects (NNT 11).

Why it matters

This was one of the most rigorous early systematic reviews of cannabinoids for chemotherapy-induced nausea and vomiting. By quantifying both benefits and harms with numbers needed to treat, it provided clinicians with practical data for decision-making. The finding that patients strongly preferred cannabinoids despite side effects suggested the anti-nausea benefit was highly valued by people undergoing chemotherapy.

The numbers in context

NNT 6 for complete nausea control. NNT 8 for complete vomiting control. NNT 3 for patient preference. Side effects: dizziness NNT 3, "high" NNT 3, sedation NNT 5, euphoria NNT 7, low blood pressure NNT 7, dysphoria NNT 8, withdrawal due to side effects NNT 11, hallucinations NNT 17, paranoia NNT 20. Relative risk for efficacy vs. conventional antiemetics: 1.38 for nausea, 1.28 for vomiting.

How the study worked

This was a quantitative systematic review with comprehensive searching across Medline, Embase, the Cochrane Library, and bibliographies in any language through August 2000. Thirty randomized comparisons with dichotomous efficacy and harm data were included, covering 1,366 patients. All tested oral nabilone, oral dronabinol, or intramuscular levonantradol against placebo or conventional antiemetics. No study used smoked cannabis.

What this study cannot tell us

None of the included trials used smoked cannabis, so results apply only to oral and intramuscular pharmaceutical cannabinoids. The comparator antiemetics were older drugs; no trials compared cannabinoids with newer 5-HT3 antagonists. Follow-up lasted only 24 hours. The trials were conducted primarily in the 1970s-1990s with varying quality standards.

How to read the evidence

This is a quantitative systematic review of 30 randomized trials with 1,366 patients, representing strong evidence through rigorous synthesis.

When this study was published

Published in 2001, this review covered trials from the 1970s-1990s. Modern antiemetics have since changed the treatment landscape.

The bigger picture

This review helped establish the evidence base for the continued use of dronabinol and nabilone as antiemetics, which remain approved for chemotherapy-induced nausea. However, the development of 5-HT3 receptor antagonists (ondansetron and similar drugs) in the 1990s provided alternatives with fewer psychoactive side effects, limiting the role of cannabinoids to patients who do not respond adequately to newer antiemetics.

Questions still open

How do cannabinoids compare with modern antiemetics like ondansetron or the NK1 receptor antagonists? Would combining cannabinoids with modern antiemetics provide additional benefit? Does smoked or vaporized cannabis perform differently from the oral formulations tested in these trials?

Common questions

Are cannabinoids still used for chemotherapy nausea?

Yes. Dronabinol and nabilone remain approved for chemotherapy-induced nausea and vomiting, typically as second-line options for patients who do not respond adequately to newer antiemetics like ondansetron.

What does NNT mean?

Number Needed to Treat (NNT) indicates how many patients need to receive a treatment for one additional patient to benefit compared to the control. A lower NNT means the treatment is more effective. An NNT of 6 for nausea means treating 6 patients with cannabinoids instead of conventional drugs results in one additional patient achieving complete nausea control.

Read the original research

Cannabinoids for control of chemotherapy induced nausea and vomiting: quantitative systematic review.

BMJ (Clinical research ed.), 323(7303), 16-21

View on PubMed ↗

Citation

Tramèr, M R; Carroll, D; Campbell, F A; Reynolds, D J; Moore, R A; McQuay, H J. (2001). Cannabinoids for control of chemotherapy induced nausea and vomiting: quantitative systematic review.. BMJ (Clinical research ed.), 323(7303), 16-21.