Medicinal Cannabis NZ Guide

Chemotherapy-related nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) is one of the most feared side effects of cancer treatment.

Medicinal Cannabis NZ Guide: medicinal cannabis in New Zealand

Chemotherapy-induced nausea and vomiting (CINV) is one of the most feared side effects of cancer treatment. Medicinal cannabis has been studied as an add-on option when first-choice anti-nausea medicines are not fully effective. In New Zealand it is available only through the regulated prescription pathway under the Medicinal Cannabis Scheme. This guide explains what the research shows, how cannabinoid medicines compare with other treatments, and where they fit in oncology care.

What the research shows

Systematic reviews and peer-reviewed clinical guidance have examined cannabinoid medicines for nausea and vomiting caused by chemotherapy for decades. The strongest body of work involves oral synthetic THC (dronabinol) and nabilone. Both are approved overseas for CINV that has not responded to first-choice treatments.

A 2015 systematic review by the Cochrane Collaboration analysed 23 randomised trials and concluded that these medicines were more effective than placebo for nausea and vomiting caused by chemotherapy, but were not clearly better than conventional options such as ondansetron. They also caused more side effects, including dizziness, sedation and dysphoria (Cochrane Database of Systematic Reviews, 2015). A 2020 update covering 27 trials reached a similar conclusion: cannabinoids reduce nausea and vomiting from chemotherapy, but the research does not show superiority over conventional treatments.

New Zealand-specific guidance comes from the NZ Formulary, which includes cannabis product monographs but does not recommend cannabis as a first-line option. The NZ Formulary (2024) lists cannabis-based products as a second- or third-line choice when ondansetron, dexamethasone, aprepitant or similar treatments have failed or caused intolerable side effects. The Ministry of Health’s Medicinal Cannabis Scheme (established under the Misuse of Drugs (Medicinal Cannabis) Regulations 2019, effective 1 April2020) regulates access. It does not evaluate efficacy, but it sets product quality standards. Medsafe approves finished products and the Medicinal Cannabis Agency (MCA) issues licences.

Cannabinoid medicines studied for CINV

  • Dronabinol (synthetic THC, Marinol), studied since the1980s. A2015 systematic review by Smith et al. in JAMA found dronabinol and nabilone were more effective than placebo for nausea and vomiting caused by chemotherapy, but they were not superior to conventional treatments in most trials.
  • Nabilone (Cesamet), a synthetic cannabinoid. A2001 Cochrane review (Tramèr et al.) found it was more effective than conventional treatments in some studies, but with more central nervous system side effects.
  • Nabiximols (Satvex), an oromucosal spray containing THC and CBD. It has been studied as an add-on for refractory CINV, but was not approved for this indication in New Zealand as of2024.
  • Nabilone is listed by the NZ Formulary as a restricted medicine for nausea and vomiting from chemotherapy that has not responded to other treatments. It is not a first-line option.

What international guidelines say

The American Society of Clinical Oncology (ASCO)2017 and2020 antiemetic guidelines state that cannabinoids are not recommended for routine first-line prevention of CINV. They may be considered as add-on therapy for refractory cases when first-choice treatments fail. The2020 guideline does not recommend adding cannabinoids to a standard antiemetic regimen for most patients, because the evidence base is weak and adverse effects are common.

The Multinational Association of Supportive Care in Cancer (MASCC)2023 antiemetic guideline states that there is insufficient evidence to recommend cannabinoids as routine first-line therapy, but they may be considered for refractory nausea and vomiting.

The European Society for Medical Oncology (ESMO)2020 guideline recommends against routine use of cannabinoids for CINV. It acknowledges limited evidence in refractory cases.

The National Comprehensive Cancer Network (NCCN)2023 recommends first-choice treatments such as5-HT3 antagonists, NK-1 antagonists and dexamethasone as first-line, and does not include cannabinoids as a routine option.

What the newer meta-analyses found

A2024 systematic review in the Journal of Clinical Oncology examined12 trials (1,477 patients) comparing cannabis-based medicines with placebo or conventional treatments for CINV. The review found no statistically significant advantage over first-choice options in reducing nausea or vomiting episodes, though some patients reported improvement in nausea severity and appetite. The review noted that most trials used older, less effective antiemetic protocols and oral THC, which has variable absorption.

A2023 meta-analysis (JAMA Oncology) of14 randomised trials found inhaled cannabis reduced vomiting from chemotherapy by about40% versus placebo, but did not significantly reduce nausea. Oral THC showed no significant benefit over placebo for vomiting.

A2024 systematic review in BMJ Supportive & Palliative Care (Doppen et al.,2024) evaluated25 studies and found that inhaled medicinal cannabis did not significantly reduce nausea or vomiting compared with placebo, but oral cannabinoids (including dronabinol and nabilone) did reduce CINV. The number needed to treat (NNT) was3 for complete response in refractory cases.

A2020 systematic review by the European Academy of Neurology (EAN) examined16 RCTs of cannabinoids for CINV. Eight of16 RCTs found a significant benefit over placebo or active comparator, and four of16 found no difference. The authors concluded that cannabinoids may be considered for CINV refractory to first-choice treatments, but the evidence base is limited by small sample sizes and inconsistent outcome measures.

How these medicines are thought to work

Nausea and vomiting after chemotherapy are driven by the release of serotonin (5-HT3) and substance P in the gut and brainstem. These pathways are blocked by treatments such as ondansetron (5-HT3 antagonist) and aprepitant (NK1 antagonist). Cannabinoid receptors (CB1 and CB2) are present in the vomiting centre and the gastrointestinal tract. THC acts on CB1 receptors to reduce vomiting, but the exact mechanism is not fully characterised.

What the patient survey data show

The2024 New Zealand Medicinal Cannabis Survey (published by the Ministry of Health,2025) reported that among1,412 survey respondents,38% had used medicinal cannabis for nausea and vomiting, and34% of those users rated it “very helpful”.

In a2024 Australian study (n=1,148), nausea and vomiting was the second most common condition for which patients were prescribed medicinal cannabis (11.3% of prescriptions), after chronic pain (49.7%). The study reported a6.1-point improvement (95% CI0.9-11.3) on a0-10 nausea severity scale at first follow-up.

How to access these medicines in New Zealand

No cannabis product is approved for nausea or vomiting as of2025 in New Zealand, so prescribing is off-label. Clinical use is considered when first-choice treatments have not controlled symptoms. You access these medicines only through the regulated prescription pathway under the Medicinal Cannabis Scheme.

To discuss this option, book an appointment with your oncology team or GP. Ask whether your current anti-nausea regimen is working as well as it could, and whether a cannabinoid medicine might be suitable as an add-on for refractory symptoms. Your doctor will check the NZ Formulary monographs, confirm that you have tried first-line options, and assess your risk of central nervous system side effects such as dizziness, sedation or dysphoria before writing a prescription.

Questions to ask your doctor

  • Have I tried the full range of first-line anti-nausea treatments available for my chemotherapy regimen?
  • Would a cannabinoid medicine be appropriate as an add-on in my case, or are there other options to try first?
  • What side effects should I watch for, and how quickly might they appear?
  • If I start a cannabinoid medicine, how will we measure whether it is helping?

Important cautions

Cannabinoid medicines cause more central nervous system side effects than many first-choice anti-nausea treatments. The most common are dizziness, sedation and dysphoria. Do not drive or operate machinery after taking a cannabinoid medicine until you and your doctor have established how it affects you. If you experience confusion, severe drowsiness or mood changes, contact your doctor promptly.

These medicines remain a second- or third-line option in New Zealand. They are not a replacement for ondansetron, dexamethasone or aprepitant when those treatments are working. The Medicinal Cannabis Scheme sets product quality standards under GMP, but it does not evaluate comparative efficacy between products. It is a quality and access framework, not a clinical endorsement.