Trends in the utilization of opioid analgesics in Australia from 1990 to 2014, by medicine formulation: (A) codeine, (B) oxycodone (note: ampoule and oxycodone + paracetamol + aspirin omitted due to low use), (C) tramadol (note: injection and oral drops omitted due to low use), (D) methadone, (E) morphine (note: sachet and combination products with tacrine and aspirin omitted due to low use), (F) fentanyl, (G) buprenorphine, (H) hydromorphone. Note the different scales between graphs. Key regulatory and subsidy changes are indicated numerically and listed in Table 2. A more exhaustive list of changes to opioid approval and subsidy can be found in Supporting Figures S1 and S2 and Table S1