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Medical cannabis reasonably safe for chronic pain management

Patients with previous cannabis use experienced significant improvement in chronic pain, according to findings published in the Journal of Pain.

Mark A. Ware, MBBS, MRCP, MSc, departments of anesthesia and family medicine, McGill University, Montreal, and colleagues reported that their prospective cohort study also demonstrated a "reasonable" safety profile for quality-controlled cannabis.

The study, part of the Cannabis for the Management of Pain: Assessment of Safety Study (COMPASS), included 215 patients with chronic pain who used cannabis (12.5% tetrahydrocannabinol) by their method of choosing and 216 controls with chronic pain who did not use cannabis.

Mark A. Ware

The researchers evaluated serious adverse events, nonserious adverse events, pulmonary function, neurocognitive function, hematology, biochemistry, renal function, liver function and endocrine function, as well as measures of pain, mood and quality of life via various tests, guidelines, scales and questionnaires. Ware and colleagues stated that patients were followed for 1 year; patients using cannabis made six clinical visits and received three telephone interviews, while patients not using cannabis made two clinical visits and received five telephone interviews.

Results showed no differences in terms of serious adverse events, pulmonary function, neurocognitive function, hematology, biochemistry, renal function, liver function or endocrine function. Patients who used cannabis were more likely to experience a nonserious adverse event (adjusted incidence rate ratio = 1.73; 95% CI, 1.41-2.13) compared with control patients. Patients who used cannabis also experienced reduced pain intensity and improved mood and quality of life, compared with controls.

According to the researchers, the median daily dose of cannabis in the cannabis group was 2.5 g per day.

"Our data show that daily cannabis users had no greater risk than nonusers (control group) to experience serious adverse events," Ware said in a press release. "We found no evidence of harmful effects on cognitive function, or blood tests among cannabis consumers and we observed a significant improvement in their levels of pain, symptom distress, mood and quality of life compared to controls."

Ware and colleagues noted that the study did not address all aspects of safety, including safety concerns in naive users.

"Moreover, long term effects on pulmonary functions and neurocognitive functions beyond one year cannot be determined," they wrote. "Further studies with systematic follow-up are required to characterize safety issues among new cannabis users, and should be extended to allow estimation of longer term risks." – by Chelsea Frajerman Pardes

Disclosures: The study was funded by the Canadian Institutes of Health Research (MOL-66262). Ware receives salary support from the FRQS and the Louise and Alan Edwards Foundation and has a research grant to his institution from CanniMed. Please see the full study for a list of all other authors' relevant financial disclosures.