Opioid Prescribing in Canada following the Legalization of Cannabis: A
Clinical and Economic Time Series Analysis
Abstract
Rationale, aims and objectives: Between January 2016 and March 2019, an
estimated 12,800 Canadians died from an opioid-related overdose. A
contributing factor has been the abuse of legally obtained prescription
opioids. The use of plant derived cannabinoids for chronic pain has been
growing in recent years. In October 2018, recreational cannabis became
legal in Canada, which resulted in increased access and a reduction in
the stigma associated with usage. The purpose of this study was to
assess trends in the amount and total cost of opioid prescribing in
Canada prior to and following cannabis legalization. Methods: National
monthly prescription claims data for public and private payers were
obtained from January 2016 to June 2019. The drugs evaluated consisted
of morphine, codeine, fentanyl, hydrocodone, hydromorphone, meperidine,
oxycodone, tramadol and the non-opioids gabapentin and pregabalin. All
opioid volumes were converted to a mean morphine equivalent dose
(MED)/claim. Gabapentin and pregabalin claims data were analyzed
separately from the opioids. Time series regression modelling was
undertaken with dependent variables being mean MED/claim and total
monthly spending. The slopes of the time series curves were then
compared pre vs. post cannabis legalization. Results: Over the 42-month
period, the mean MED/claim declined within public plans (p <
0.001). However, the decline in MED/claim was 5.4 times greater in the
period following legalization (4.1 vs. 22.3 mg/claim). Total monthly
opioid spending by public payers was also reduced to a greater extent
post legalization ($95,000 vs. $267,000 per month). The findings were
similar for private drug plans; however, the absolute drop in opioid use
was more pronounced (30.8 mg/claim pre vs. 76.9 mg/claim post). Over the
42-month period, gabapentin and pregabalin usage also declined.
Conclusions: Our findings support the hypothesis that easier access to
cannabis for pain may reduce opioid use for both public and private drug
plans.