Guideline gives weak support to trying oral medical cannabis for chronic pain



“Evidence alone is not sufficient for clinical decision-making, particularly in chronic pain,” said Jason Busse, DC, PhD, director of Michael G. DeGroote Centre for Medicinal Cannabis Research at McMaster University, Hamilton, Ont., and lead author of a newly released rapid guideline on medical cannabis or cannabinoids for chronic pain.

Dr. Jason Busse, McMaster University McMaster University

Dr. Jason Busse

The recommendations, published online Sept. 9, 2021 in the British Medical Journal, suggest that providers offer patients with chronic pain a trial of noninhaled medical cannabis or cannabinoids if standard care or management is ineffective. However, the “weak” rating attached to the recommendation may compel some clinicians to automatically write off the panel’s recommendations.

“Because of the close balance between benefits and harms and wide variability in patient attitudes, the panel came to the conclusion that [some] patients presented with the current best evidence would likely choose to engage in a trial of medicinal cannabis, if their current care was felt to be suboptimal,” Dr. Busse explained in an interview.

But more importantly, “the recommendation allows for shared decision making to occur, and for different patients to make different decisions based on individual preferences and circumstances,” he said.

Evidence supports improved pain and sleep quality, physical functioning

Evidence supporting the use of medical cannabis in chronic pain is derived from a rigorous systematic review and meta-analysis of 32 studies enrolling 5,174 patients randomized to oral (capsule, spray, sublingual drops) or topical (transdermal cream) medical cannabis or placebo. Of note, three types of cannabinoids were represented: phytocannabinoids, synthetic, and endocannabinoids.

cannabis products with leaf, capsules and CBD oil rgbspace/Getty Images

The studies included both patients with chronic noncancer pain (28 studies, n = 3,812) and chronic cancer pain not receiving palliative care (4 studies, n = 1,362). On average, baseline pain scores were a median 6.28 cm on a 10-cm visual analog scale (VAS), and median participant age was 53 years. 60% of trials reporting sex differences enrolled female participants. Overall, patients were followed for roughly 2 months (median, 50 days).

Findings (27 studies, n = 3,939) showed that, compared with placebo, medical cannabis resulted in a small, albeit important, improvement in the proportion of patients experiencing pain relief at or above the minimally important difference (MID) (moderate-certainty evidence, 10% modeled risk difference [RD; 95% confidence interval, 5%-15%] for achieving at least the MID of 1 cm).

Medical cannabis (15 studies, n = 2,425) also provided a small increase in the proportion of patients experiencing improvements in physical functioning at or above the MID (high certainty evidence, 4% modeled RD [95% CI, 0.1%-8%] for achieving at least a MID of 10 points).

Additionally, participants experienced significant improvements in sleep quality, compared with placebo (16 studies, 3,124 participants, high-quality evidence), demonstrating a weighted mean difference of –0.53 cm on a 10-cm VAS (95% CI, –0.75 to –0.30 cm). A total of nine larger trials (n = 2,652, high-certainty evidence) saw a small increase in the proportion of patients experiencing improved sleep quality at or above the MID: 6% modeled RD (95% CI, 2%-9%).

On the other hand, benefits did not extend to emotional, role, or social functioning (high-certainty evidence).


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