Transition to high-dose or strong opioids: a population-based study of people initiating opioids in Australia

Background and aims Strong and high-dose opioids are associated with opioid overdose and death. The objective of this study was to determine the rate and predictors of transitioning to high-dose or strong opioids among people initiating opioids. Design Retrospective cohort study. Setting Australia. Participants People initiating opioid analgesics from July 2013 to January 2018 were identified from a random 10% sample of Australia's Pharmaceutical Benefits Scheme eligible population. Measurements Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for the predictors of escalating to >= 50 mg oral morphine equivalents (OMEs)/day (cohort 1); >= 90 mg OMEs/day (cohort 2) and transitioning from weak opioids to strong opioids (cohort 3) over 12 months of follow-up. Predictors included age, sex, number of comorbidities, history of depression, prior treatment for cancer and selected other medication use. Findings In total, 861 691 people initiated opioids at average doses < 50 mg OMEs/day (cohort 1), 874 401 at < 90 mg OMEs/day (cohort 2) and 603 884 initiated weak opioids (cohort 3). Overall, 1.4% of people escalated to doses >= 50 mg OMEs/day, 0.8% to doses >= 90 mg OMEs/day and 7.3% transitioned to strong opioids. The strongest predictors of transitioning included prior treatment for cancer [cohort 1: HR = 3.19, 95% CI = 3.00-3.40; cohort 2: HR = 4.19, 95% CI = 3.90-4.51; cohort 3: HR = 2.07, 95% CI = 1.95-2.18] and age >= 75 years (cohort 1: HR = 3.04, 95% CI = 2.73-3.38; cohort 2: HR = 2.51, 95% CI = 2.17-2.89; cohort 3: HR = 1.88, 95% CI = 1.80-1.96). Females transitioned to high doses and strong opioids less rapidly than males (cohort 1: HR = 0.79, 95% CI = 0.76-0.82; cohort 2: HR = 0.70, 95% CI = 0.66-0.73; cohort 3: HR = 0.95, 95% CI = 0.93-0.96). Conclusions In Australia, more than one in every 13 people initiating weak opioids transition to strong opioids. By extrapolation, more than 26 000 Australian adults initiating opioids escalate to high doses each year. People with cancer treatment history, older people and males transition to strong and high-dose opioids more rapidly than others.