Opioid Initiation in Older Patients with Chronic Pain Who Received Authorized Cannabis Prescription.

BACKGROUND: Cannabis is being increasingly used to treat chronic pain, with studies suggesting that concurrent use with opioids may reduce the need for opioid medications. However, specific to opioid-naïve patients, the effects of cannabis exposure on opioid initiation are not well known.

OBJECTIVE: To assess the association between the authorized prescription of cannabis and opioid initiation in older patients with chronic pain.

STUDY DESIGN: We conducted a cohort study of Ontario patients aged 66 years and older with chronic pain, without a dispensation of opioids in the past year. Patients who received an authorized prescription of cannabis between 2014 and 2019 were compared with population-based controls. Clinical data combined with Ontario medical administrative data were used to conduct the analyses. The study outcome was defined as opioid dispensations covering ≥90 days in the year following the authorized prescription of cannabis. Inverse probability of treatment weighting was used to minimize confounding, and weighted Poisson regressions were used to calculate risk ratios.

RESULTS: In total, 3427 exposed patients and 12006 controls were included. The rates of the outcome (i.e., initiating opioid covering ≥90 days) were 1.84 and 1.19/100 person-years, respectively, in the exposed and the controls. The adjusted risk ratio (RR) was 1.54 (95% CI: 1.07-2.23). The risk was significant in male patients (RR: 1.82 (1.09-3.04)) and non-significant in females (RR: 1.35 (0.84-2.17).

CONCLUSION: Results suggest that opioid-naïve older patients with chronic pain, initiating medical cannabis, were at higher risk of opioid initiation in the year following cannabis prescription.