Cannabinoids Reduce Acute Pain Score More Than Placebo

Herman Johal, MD, MPH, PhD

Findings of a recent systematic review showed a small but significant reduction in subjective pain scores for cannabinoid treatment compared to placebo in patients who experienced acute pain.

Herman Johal, MD, MPH, PhD, and a team of Canada-based investigators analyzed 6 trials to find the best evidence of the efficacy of cannabinoids for acute pain in clinical settings based on subjective pain scores and adverse effects. The team found low-quality evidence that cannabinoids can be a safe alternative for a small but significant reduction in pain. What’s more, intramuscular administration led to a greater reduction than oral.

In their systematic review and meta-analysis, Johal, an assistant professor in the surgery department at McMaster University in Canada, and colleagues reviewed 5 trials that used oral cannabinoids and 1 that used intramuscular cannabinoids. The trials included compared cannabinoids with placebo in patients with acute pain—a distressing experience secondary to actual or potential tissue damage that lasted <3 months.

Johal and the team did not include trials focused on chronic pain or conditions associated with chronic pain; nonhuman trials or nonclinical trials; abstracts or posters from conferences; and trials with incomplete or absent pain outcome data.

The investigators collected intervention details like the type, dosage, and route of cannabinoid used, along with the study design, patient demographic information, and sample size. The team also gathers outcomes including the type of pain scale used and the mean pain score at baseline and any change.

The team’s search identified 1257 citations and 25 underwent full-text review before 6 were selected for the meta-analysis. In total, 678 participants were included across 6 randomized, placebo-controlled, parallel-group trials. Three of the studies examined multiple cannabinoid doses, leading to 11 cannabinoid intervention versus placebo comparisons.

After a review of all 11 comparisons, there was a statistically significant treatment effect for the use of cannabinoids (-.9; 95% CI, -1.69 to -.1; P=.002). There were 5 studies that reported on oral cannabinoids, which showed no significant effect when compared with placebo (-.21; 95% CI, -.64 to .22; P=.41).

In the 1 study that evaluated intramuscular administration of cannabinoids, there was a significant effect which favored the use of cannabinoids over placebo (-2.98; 95% CI, -4.09 to -1.87; P <.0001).

Participants across all 6 trials reported adverse effects in the placebo and cannabinoid cohorts. There were 437 events in 374 patients (1.17 adverse events/patient) in the cannabinoid sample and 309 side effects in 304 patients in the control arm (1.02 adverse events/patient).

There was a significantly higher incidence of dizziness and hypotension in the cannabinoid group, but overall, there was no significant difference in serious adverse effects (OR, 1.44; 95% CI, .6-3.48).

Serious adverse effects in the treatment group were nausea, headache, sedation, dysphagia, and pharyngolaryngeal pain. In the placebo group, adverse events included headache, nausea, myalgia, pain, and swelling.

Additional research should investigate the optimal route and composition of cannabinoids in the acute pain setting to better understand risks and benefits of cannabinoids in the patient population, the investigators suggested.

The study, “Cannabinoids in the Management of Acute Pain: A Systematic Review and Meta-analysis,” was published online in the journal Cannabis and Cannabinoid Research.