Trends in licit opioid use in Australia, 1984-1998: comparative analysis of international and jurisdictional data

OBJECTIVES: To examine trends from 1984 to 1998 in licit opioids used in Australia compared with nine other developed countries, and in New South Wales compared with other Australian jurisdictions. DESIGN: Poisson regression analysis of annual rates of national and jurisdictional consumption of methadone, morphine and pethidine. MAIN OUTCOME MEASURES: All drug data were standardised to defined daily doses per 1000 population per day. RESULTS: Methadone consumption increased by, on average, 12% per year (RR, 1.12; 95% CI, 1.08-1.17), with Australia in the first rank of countries. Morphine use increased by 5% per year (RR, 1.05; 95% CI, 1.02-1.09), with Australia ranking equal second with three other countries behind Denmark. Consumption of pethidine in all 10 countries was unchanged (RR, 0.99; 95% CI, 0.97-1.00), with Australia equal first. In Australia, use of methadone syrup increased by 17% per year (RR, 1.17; 95% CI, 1.16-1.17) and by 11% per year for methadone tablets (RR, 1.11; 95% CI, 1.10-1.12). Consumption of methadone syrup in NSW was more than double that of any other jurisdiction. Consumption of methadone tablets was 2.4 times higher in South Australia (RR, 2.35; 95% CI, 2.09-2.65) than NSW. The Northern Territory, Tasmania and Queensland also had significantly higher consumption than NSW. From 1991 to 1998, controlled-release morphine consumption increased by 27% per year nationally (RR, 1.27; 95% CI, 1.24-1.30). The NT had 2.6 times more supply of morphine (RR, 2.63; 95% CI, 1.71-4.03) and Tasmania 58% more supply than NSW (RR, 1.58; 95% CI, 1.11-2.25). CONCLUSIONS: Australia's consumption of licit opioids ranked high internationally. There were diverse trends in the supply of licit opioids to Australia's jurisdictions, resulting in a heterogeneous pattern throughout the country.