Initiation of strong prescription opioids in Australia: cohort characteristics and factors associated with the type of opioid initiated

Abstract

AIMSTo describe the characteristics of Australians initiating strong opioids and examine the factors associated with the type of opioid initiated. METHODSPharmaceutical Benefits Scheme dispensing records were extracted for a 10% sample of people who initiated a strong opioid treatment episode (buprenorphine, fentanyl, hydromorphone, morphine, oxycodone) between 29 September 2009 and 31 December 2013, as evidenced by the absence of a strong opioid dispensing for at least 90 days. The cohort was restricted to people with complete medicines ascertainment. Socio-demographic characteristics, previous dispensing histories and index opioid use were examined. Multinomial logistic regression was used to calculate adjusted relative risk ratios (aRRRs) and 95% confidence intervals (CIs) to determine the factors associated with the type of opioid medicine initiated, relative to oxycodone. RESULTSThe cohort consisted of 125 335 people: 58.3% were female and 63.7% were aged ≥65 years. The most commonly initiated strong opioid was oxycodone (72.8%), usually 5 mg immediate-release tablets (76.1%). Compared to people aged 18-44 years, those ≥85 years were 14.18 times as likely (95% CI 12.67-15.87) to initiate morphine than oxycodone. Compared to people without a cancer treatment history, those with a cancer treatment history were 2.34 times as likely (95% CI 2.11-2.60) to initiate morphine than oxycodone. CONCLUSIONSThe most commonly initiated strong opioid was oxycodone, usually at lower strengths. Those who initiated oxycodone were more likely to be younger with no previous cancer treatment history. As these are high-risk characteristics for potential harms, a judicious approach when initiating strong opioids for this group is necessary.

Prevalence and incidence of prescription opioid analgesic use in Australia

“…Use of paracetamol, pregabalin and the PBS-subsidized nonsteroidal anti-inflammatory drugs (NSAIDs) were examined in the 3 months prior to and including the day of opioid initiation, in order to determine the recent non-opioid analgesic treatment of pain. This definition is consistent with previous published studies [11]. NSAIDs were further categorized into nonselective and cyclooxygenase 2 selective (Appendix Table A1).…”

“…We mapped the RxRisk‐V tool to the International Classification of Diseases, Tenth Revision (ICD‐10). To group these disease categories, we matched them to ICD‐10 chapter groupings, as has been done in a previous study utilizing PBS data . The RxRisk‐V tool identifies fewer people with cancer than the Charlson's Comorbidity Index (43.2% vs .…”

“…Opioid‐related deaths appear most common in people aged <50 years . Previous work examining strong opioid initiation among concessional beneficiaries in Australia identified that oxycodone was the most commonly initiated strong opioid, and that those initiating oxycodone were younger and less likely to have cancer . The Australian Pain and Opioids In Treatment (POINT) study has found that people with CNCP taking opioids have complex demographic and clinical profiles, and a long history of pain .…”

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

“…This suggests that the primary contributors to the increases in oxycodone use were an expanding population of people prescribed oxycodone, who were most likely to be prescribed lower average doses. In support of these conclusions, marked increases in the treatment of opioid naïve individuals with oxycodone have been observed in the community, hospital inpatient settings, emergency departments, and upon hospital discharge, with the vast majority of these individuals treated with low doses and for short durations . Use of low strength formulations has further increased since the PBS subsidy of oxycodone/naloxone in 2011 …”

Identifying incident cancer cases in dispensing claims

“…Several Australian studies have used the dispensing of anticancer medicines as a proxy for incident cancer [ 15 , 16 ], notably studies investigating patterns of opioid use [ 17 - 19 ]. While the use of this proxy is common and intuitively supported by the specific indications of anticancer medicines—few, if any, of these agents are indicated for conditions other than cancer— its validity has not been investigated comprehensively nor are the implications of applying such a proxy well understood.…”