Twenty-five years of prescription opioid use in Australia

In this item Dr Emily Karanges discusses her paper which won the HSRAANZ award for the Best Paper by an early career researcher.

The importance of prescription opioids in the treatment of pain is indisputable, but the increases in opioid use observed globally over the last two decades have generated considerable concern. North America is currently experiencing a ‘prescription opioid epidemic', with misuse and abuse, dependence, overdose and deaths increasing with burgeoning use. Opioid use and harms have also increased in Australia. In 2014, approximately 13% of Australians were dispensed prescription opioids.

This paper provides a comprehensive account of prescription opioid use in Australia over 25 years, from 1990. It uses data on opioid prescriptions dispensed primarily from community pharmacies and private hospitals, including those subsidised under the Pharmaceutical Benefits Scheme (PBS) and Repatriation Pharmaceutical Benefits Scheme (RPBS) and unsubsidised prescriptions (medicines priced under the general patient co-payment and private prescriptions; the latter until mid-2012). Opioid use is presented in defined daily doses per 1000 population per day (DDD/1000 pop/day), where a defined daily dose is said to represent the mean daily dose of the drug when used for its main indication in adults.

The study also examined some of the factors influencing increasing opioid use, mapping trends against regulatory changes instigated by the Therapeutic Goods Administration (TGA) and changes to PBS subsidy.

The results describe a 4-fold increase in opioid use between 1990 and 2014, from 4.6 to 18.0 DDD/1000 pop/day. There was a clear shift from short- to long-acting opioids, and from weaker opioids (i.e. codeine, dextropropoxyphene and tramadol) to stronger opioids. In 1990, approximately 95% of opioids were short-acting formulations, and the weaker opioids codeine and dextropropoxyphene comprised 90% of total use. The balance shifted with morphine and methadone use increasing more than 10-fold over the 1990s and tramadol, oxycodone, buprenorphine, fentanyl, and hydromorphone use growing over the 2000s. By 2011, use of stronger opioids had increased 15-fold and long-acting formulations accounted for half of prescription opioid use.

Many of these trends were facilitated by changes in medicine subsidy, while regulatory changes had little immediate impact on the use of a given opioid or formulation. For example, the subsidy rather than availability of long-acting morphine in 1991/2 and tramadol in 2001 coincided with the precipitous rise in their use. Similarly, expansion of subsidy restrictions from the treatment of cancer pain to non-cancer pain markedly increased opioid use. This was instrumental in the rise of fentanyl transdermal patches, for example; use was minimal prior to its 2006 subsidy for chronic non-cancer pain (CNCP), despite subsidy for cancer pain since 1999.

Current guidelines support the use of long-acting opioids in pain control and there is strong evidence for the effectiveness of opioids in the short-term treatment of CNCP. With the uncertainty about the long-term efficacy of opioids in chronic non-cancer pain and Australia’s current attempts to curb opioid use and harms, the impact of evidence-based changes in medicine subsidy should not be overlooked.

https://www.ncbi.nlm.nih.gov/pubmed/26991673

http://onlinelibrary.wiley.com/wol1/doi/10.1111/bcp.12937/full

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Dr Emily Karanges is a research fellow in the Medicines Policy Research Unit within the Centre for Big Data Research in Health. Her research focus concerns the pharmacoepidemiology of psychotropic medicine use. While her research extends to all age groups, Emily has a particular interest in the use of psychotropics in children, adolescents and young adults. She is also interested in the pharmacoepidemiology of opioid analgesics.  Emily also has expertise in the field of psychopharmacology. In 2015 she received her PhD in behavioural neuroscience, psychopharmacology and psycho-pharmacoepidemiology at the University of Sydney. Her thesis was primarily concerned with the behavioural and neurobiological effects of antidepressant treatment during adolescence.