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PainMay 2, 2023

Researchers say medicinal cannabis helps to relieve cancer pain and cuts opioid prescriptions

Prescribing medicinal cannabis to relieve cancer pain appears to be a safe option, the results of a multicentre registry study that was published online in BMJ Supportive & Palliative Care today (3 May) suggest.

Medicinal cannabis also helps to reduce the total number of medication and opioids taken by patients, according to a research team that included Antonio Vigano, from the Supportive and Palliative Care Division at the McGill University Health Centre in Montreal, Quebec.

Products with an equal balance of the active ingredients tetrahydrocannabinol (THC) and cannabidiol (CBD) – rather than a dominance of either one – seem to be particularly effective, Dr Vigano and his colleagues note. They suggest that medicinal cannabis is a safe and complementary treatment when conventional drugs fail to touch cancer-related pain.

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Medicinal cannabis: a 'safe and complementary treatment option' for patients with cancer


Patients’ pain intensity and other factors monitored

The research team studied the treatment responses of 358 adults with cancer whose details were submitted to a multicentre registry – the Quebec Cannabis Registry in Canada – over a period lasting three and a half years (May 2015-October 2018).

The patients’ average age was 57; nearly half (48 per cent) were men; and the three most common cancer diagnoses were genitourinary, breast, and bowel. Pain was the most frequently reported (72.5 per cent) symptom that prompted a prescription of medicinal cannabis. THC-dominant, THC:CBD-balanced, and CBD-dominant products were authorised in 24.5 per cent, 38 per cent, and 16.5 per cent of patients, respectively. Taking the product by mouth was the most frequently recommended route (59 per cent). 

Our data suggest a role for [medicinal cannabis] as a safe and complementary treatment option in patients with cancer failing to reach adequate pain relief through conventional analgesics, such as opioids [Saro Aprikian et al]

Pain intensity

Patients’ pain intensity, symptoms, total number of drugs taken, and daily morphine consumption were monitored quarterly for one year. Pain intensity was rated, using validated measures, on a sliding scale from none (zero) to the worst possible (10), and pain relief from none (0 per cent) to complete (100 per cent), with two summary measures of overall pain severity and pain interference over the preceding 24 hours.

Medicinal cannabis seemed to be safe and well tolerated, with only 15 side effects (rated as moderate to severe) reported by 11 patients, 13 of which were regarded as minor. The two most common side effects were sleepiness, reported by three patients, and fatigue, reported by two. 

Close supervision of patients was helpful

Two serious side effects (pneumonia and a cardiovascular event) were deemed unlikely to have been linked to medicinal cannabis. Only five patients stopped taking medicinal cannabis because of side effects. ‘The particularly good safety profile of [medicinal cannabis] found in this study can be partly attributed to the close supervision by healthcare professionals who authorised, directed, and monitored [the] treatment,’ Dr Vigano and his colleagues state.

Statistically significant decreases were observed at three, six and nine months for worst and average pain intensity, overall pain severity, and pain interference [with daily life] Overall, THC:CBD balanced products were associated with better pain relief than either THC-dominant or CBD-dominant products. The total number of drugs taken also fell consistently at all the subsequent quarterly check-ups, while opioid use fell over the first three check-ups.


As this study was observational in nature, cause cannot be established, the researchers acknowledge. Moreover, a significant number of patients was lost to follow-up over the course of the 12 months, while information on the use of other prescribed medication was limited to addition or discontinuation, the authors note. 

They conclude: ‘Our data suggest a role for [medicinal cannabis] as a safe and complementary treatment option in patients with cancer failing to reach adequate pain relief through conventional analgesics, such as opioids.’


More than half of patients undergoing anti-cancer treatment and two thirds of those with advanced or terminal disease experience pain, the researchers state.

Powerful opioids along with other medication – such as anti-inflammatory and anticonvulsant drugs – are usually prescribed for pain relief. 

But one patient in three will still experience pain, while the side effects of opioids include nausea, sleepiness, constipation, and respiratory depression.

To see the full version of the paper – titled Medical cannabis is effective for cancer-related pain: Quebec Cannabis Registry results doi 10.1136/spcare-2022-004003 – click

Author: Ian A McMillan
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