December 09, 2015
The Journal of Pain: Official journal of the American Pain Society
TAKE-HOME MESSAGE
A cohort of 215 current or previous users of medical cannabis with non-cancer pain were dispensed an herbal cannabis product and were then matched with 216 controls with chronic pain but not using cannabis. After 1-year follow-up with a median dose of 2.5 g/day of cannabis in the user group, there was no significant difference in the rate of serious adverse events between the two groups. The cannabis users did report a higher incidence of mild to moderate adverse events, the most common event being a headache.
Patients with experience of cannabis use can safely use quality-controlled herbal cannabis in the treatment of chronic non-cancer pain in the short term, but further research is needed to assess the long-term outcomes.
Abstract
Cannabis is widely used as a self-management strategy by patients with a wide range of symptoms and diseases including chronic non-cancer pain. The safety of cannabis use for medical purposes has not been systematically evaluated. We conducted a prospective cohort study to describe safety issues among individuals with chronic non-cancer pain. A standardized herbal cannabis product (12.5% tetrahydrocannabinol) was dispensed to eligible individuals for a 1-year period; controls were individuals with chronic pain from the same clinics who were not cannabis users. The primary outcome consisted of serious adverse events and non-serious adverse events. Secondary safety outcomes included pulmonary and neurocognitive function and standard hematology, biochemistry, renal, liver, and endocrine function. Secondary efficacy parameters included pain and other symptoms, mood, and quality of life. Two hundred and fifteen individuals with chronic pain were recruited to the cannabis group (141 current users and 58 ex-users) and 216 controls (chronic pain but no current cannabis use) from 7 clinics across Canada. The median daily cannabis dose was 2.5 g/d. There was no difference in risk of serious adverse events (adjusted incidence rate ratio = 1.08, 95% confidence interval = .57-2.04) between groups. Medical cannabis users were at increased risk of non-serious adverse events (adjusted incidence rate ratio = 1.73, 95% confidence interval = 1.41-2.13); most were mild to moderate. There were no differences in secondary safety assessments. Quality-controlled herbal cannabis, when used by patients with experience of cannabis use as part of a monitored treatment program over 1 year, appears to have a reasonable safety profile. Longer-term monitoring for functional outcomes is needed.