Prescribe Medical Cannabis to Patients with Chronic Pain, Experts Recommend

People living with chronic pain that is not properly managed by standard care interventions should be offered a trial of non-inhalable medical cannabis or cannabinoids, a panel of international experts has advised.

This new advice, produced as a part of the British Medical Journal’s (BMJ’s) Rapid Recommendations initiative to offer fast and trustworthy guidelines for clinical practice, applies to adults and children living with moderate-to-severe levels of chronic pain. It does not include the use of inhalable or smokeable medical cannabis products. The BMJ has created an interactive visual summary to illustrate the key findings of the panel.

These recommendations differ from the most recent treatment guidelines published by the National Institute for Health Care and Excellence (NICE), which gave strong recommendations against the use of medical cannabis for chronic pain outside of clinical trials.

“Weak recommendation” balances benefits and limited harms

The Rapid Recommendations panel included three patients with lived experience of chronic pain as well as general practitioners, a pediatrician, pharmacists, physicians specializing in pain management, clinical pharmacologists, and a number of other relevant medical specialists. The recommendations handed down by the panel were informed by a series of four systematic reviews targeting the current body of evidence on medical cannabis’ benefits and harms with respect to chronic pain, as well as evidence regarding patient values and preferences for medical cannabis.

Together, the four systematic reviews covered 32 randomized trials exploring the benefits and harms of medical cannabis or cannabinoids for chronic pain, 39 observational studies exploring long-term harms, 17 studies of cannabis substitution for opioids, and 15 studies of patient values and preferences.

The panel made a “weak recommendation” in support of medical cannabis use for chronic pain. The strength of the recommendation reflects the uncertainty in typical patient preferences towards cannabis use, as well as the notion that benefits will outweigh harms for most, but not all, patients.

“The recommendation is weak because of the close balance between benefits and harms of medical cannabis for chronic pain,” the experts wrote in their clinical practice guideline, published in the BMJ. “It reflects a high value placed on small to very small improvements in self reported pain intensity, physical functioning, and sleep quality, and willingness to accept a small to modest risk of mostly self limited and transient harms.”

From this review of the evidence, the Rapid Recommendations panel concluded that it had high and moderate levels of certainty in the ability of medical cannabis to affect a small increase in the proportion of chronic pain patients experiencing improvements in pain and sleep quality, respectively. However, high-quality evidence was also found showing a small to very small increase in the proportion of people with chronic pain who experienced transient harms, including cognitive impairment, vomiting, drowsiness, and impaired attention as a side effect of medical cannabis treatment.

The panel was less confident about the ability of medical cannabis to reduce the concomitant use of opioids or whether medical cannabis use could be associated with the increased risk of cannabis dependence, road traffic accidents, suicidal ideations, or other potentially serious harms. Given the lack of high-quality studies in this area, the panel recommends that additional research be done to fill in these current knowledge gaps, as well as to explore factors such as optimal dosing and the benefits and harms of inhaled cannabis.

In terms of patient attitudes, the panel found moderate to high certainty evidence that people living with chronic pain prefer high-CBD or balanced THC:CBD products, as opposed to high-THC products. Positive and negative social factors were also great influencers in a patient’s willingness to consider medical cannabis treatment, as well as general concerns over the cost of treatment or potential adverse drug effects.

More research needed to increase certainty

In a linked editorial also published in the BMJ, Canadian researchers Edeltraut Kröger and Clermont Dionne welcomed the new guidance.

“This new patient-centered guidance can improve shared decision making: clinicians should emphasize the harms associated with vaping or smoking cannabis and, as recommended by other guidelines, suggest products with known compositions such as nabilone or nabiximols, discourage self-medication, and pay particular attention to vulnerable populations,” they wrote.

While the scientists accept that this research and the resulting guidelines “fill a critical gap in information” for medical decision-making, Kröger and Dionne also point out some critical shortcomings in these meta-analyses.

They specifically highlighted the two significant meta-analyses of the randomized trials within the systematic review. One was a meta-analysis of 27 randomized controlled trials that found an increase in the proportion of patients reporting an improvement in pain of at least 1 cm on a 10 cm visual analog scale (although a minimum reduction of 1.5 cm is typically considered clinically relevant) when using medical cannabis. The second was a meta-analysis of 10 placebo-controlled trials that found a 7 percent increase in the proportion of patients reporting at least a 30 percent reduction in pain in favor of cannabis compared with placebo.

“Methodological and ethical problems in these trials limited the level of certainty in the evidence underpinning Busse and colleagues’ recommendations,” they wrote. “They include follow-up periods of less than six months (very short for chronic conditions), small sample sizes, funding by industry, and use of different outcome measures that complicate comparisons.”

These problems limit the level of certainty in the evidence which underpins the new regulations, they say. However, an ambitious program of scientific research on the short- and long-term effects of medical cannabis for specific subtypes of chronic pain could help to address these current limitations.

As it can take many years to properly determine the long-term harms or other risk factors associated with a new treatment, the scientists also advise that clinicians emphasize the known harms associated with vaping or smoking cannabis to their patients, discourage self-medication, and pay particularly close attention to vulnerable patient populations.