Trends in opioid utilisation in Australia, 2006-2015: Insights from multiple metrics.

Purpose: Population-based observational studies have documented global increases in opioid analgesic use. Many studies have used a single population-adjusted metric (number of dispensings, defined daily doses [DDDs], or oral morphine equivalents [OMEs]). We combine these volume-based metrics with a measure of the number of persons dispensed opioids to gain insights into Australian trends in prescribed opioid use. Methods: We obtained records of prescribed opioid dispensings (2006-2015) subsidised under Australia's Pharmaceutical Benefits Scheme. We used dispensing claims to quantify annual changes in use according to 3 volume-based metrics: DDD/1000 pop/day, OME/1000 pop/day, and dispensings/1000 pop. We estimated the number of persons dispensed at least one opioid in a given year (persons)/1000 pop using data from a 10% random sample of Pharmaceutical Benefits Scheme-eligible Australians. Results: Total opioid use increased according to all metrics, especially OME/1000 pop/day (51% increase) and dispensings/1000 pop (44%). Weaker opioid use remained stable or declined; strong opioid use increased. The rate of persons accessing weaker opioids only decreased 31%, and there was a 238% increase in persons dispensed only strong opioids. Strong opioid use also increased according to dispensings/1000 pop (140%), OME/1000 pop/day (80%), and DDD/1000 pop/day (71% increase). Conclusions: Our results suggest that the increases in total opioid use between 2006 and 2015 were predominantly driven by a growing number of people treated with strong opioids at lower medicine strengths/doses. This method can be used with or without person-level data to provide insights into factors driving changes in medicine use over time.