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Cannabinoids not recommended to treat cancer-related pain

No more effective than placebo; and their help with sleep problems might be short-lived as tolerance develops

Louise Prime

Tuesday, 21 January 2020

The addition of cannabinoids to opioids does not reduce cancer pain for adults with advanced cancer and they cannot be recommended for this indication, a UK-led analysis1 has shown, published today in BMJ Supportive & Palliative Care. In the same journal, a separate small study2 from Israel has found that although medicinal cannabis might have an overall positive effect on maintaining sleep throughout the night in chronic pain patients, tolerance towards its potential sleep-inducing properties might occur with frequent use.

Researchers from the Universities of Hull and Leeds conducted a systematic review and meta-analysis of randomised controlled trials (RCTs) that had compared cannabinoids with placebo/other active agents for the treatment of cancer-related pain in adults, looking at both the primary outcome of effect on pain intensity and adverse effects, including dropouts.

They reported that studies with a low risk of bias showed that for adults with advanced cancer, the addition of cannabinoids to opioids did not reduce cancer pain (in terms of change in average Numeric Rating Scale pain scores) compared with placebo. They also noted that cannabinoids were associated with an excess risk of many short-term non-serious adverse effects compared with controls, although there was no significant difference for serious adverse effects.

They concluded: “For a medication to be useful, there needs to be a net overall benefit, with the positive effects (analgesia) outweighing adverse effects… When statistically pooled, there was no decrease in pain score from cannabinoids. There are, however, significant adverse effects and dropouts reported from cannabinoids.

“Based on evidence with a low risk of bias, cannabinoids cannot be recommended for the treatment of cancer-related pain.”

In the second study, researchers recruited 128 people aged 50 years or more who had chronic neuropathic pain of organic origin, and compared sleep problems between the 66 users of medicinal cannabis (used for at least a year prior to data collection) and the 62 similar non-users. They asked participants how often during the past month they had had problems falling asleep, woken up early in the morning without being able to fall back asleep, and woken up during sleep.

They reported that after adjustment for age, sex, pain level and use of sleep and antidepressant medications, the use of medicinal cannabis was associated with less problems with waking up at night compared with non-use; there were no differences between the groups in terms of either falling asleep or waking up early without managing to fall back asleep. However, frequent medicinal cannabis use was associated with more problems waking up at night and falling asleep.

They concluded: “Medicinal cannabis use may have an overall positive effect on maintaining sleep throughout the night in chronic pain patients. At the same time, tolerance towards potential sleep- inducing properties of medicinal cannabis might occur with frequent use. More research based on randomised control trials and other longitudinal designs is warranted.”

The authors of a separate reviewpublished in the Journal of the American College of Cardiology, recommend that cardiologists screen their patients for marijuana use, asking them how often and how much they use – as well as how they use the drug, as vaping it increases its pharmacological effects – because some observational studies have suggested an association between marijuana and a range of cardiovascular risks, and marijuana is becoming increasingly potent.

Furthermore, they said, some cardiovascular medications can be affected by marijuana use, for example, statin levels can increase in the blood when used together with marijuana because both are metabolised through the cytochrome P450 system, and levels of blood thinners such as warfarin also can be expected to increase when used together with marijuana.

They commented: “Our review suggests that smoking marijuana carries many of the same cardiovascular health hazards as smoking tobacco. While the level of evidence is modest, there's enough data for us to advise caution in using marijuana for our highest-risk patients, including those who present with a heart attack or new arrhythmia, or who have been hospitalized with heart failure.”


  1. Boland EG, Bennett MI, Allgar V, et al. Cannabinoids for adult cancer- related pain: systematic review and meta- analysis. BMJ Supportive & Palliative Care Epub ahead of print: 20 January 2020. doi:10.1136/bmjspcare-2019-00203.
  2. Sznitman SR, Vulfsons S, Meiri D, et al. Medical cannabis and insomnia in older adults with chronic pain: a cross- sectional study. BMJ Supportive & Palliative Care Epub ahead of print: 20 January 2020. doi:10.1136/bmjspcare-2019-001938
  3. DeFilippis EM, Bajaj NS, Singh A, et al. Marijuana use in patients with cardiovascular disease. J Am Coll Cardiol. 2020 Jan, 75 (3) 320-332.

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