Overall trend in overdose and age most affected
The number of deaths due to opioid overdose in Australia is growing. Between 2004 and 2014, there was a 61% increase in deaths due to accidental overdose (from 705 deaths in 2004 to 1137 in 2014).13 Of the people who died in 2014, 78% were aged between 30 and 59 years.13
Geographical trend in overdose
The overall increase in overdose deaths is being driven by those occurring in rural and regional areas. Between 2008 and 2014, there was an 83% increase in deaths in these areas (from 3.1 deaths per 100,000 to 5.7 per 100,000).13 In the same time period in metropolitan areas the rate changed from 4.2 per 100,000 to 4.4 per 100,000.13
Overdose trend in Aboriginal and Torres Strait Islander peoples
Accidental deaths due to opioid overdose per capita for Aboriginal and Torres Strait Islander peoples has increased substantially. Between 2004 and 2014 there was an increase of 141% across the five jurisdictions with Aboriginal data; from 3.9 deaths per 100,000 in 2004 to 9.4 per 100,000 in 2014.13
Relationship between patient factors, opioid characteristics and overdose
Higher opioid dosages are associated with an increased risk of fatal overdose. There is a three-fold increase in mortality when comparing high-dose opioid (>200 mg oral morphine equivalent daily dose [OMEDD]) relative to low-dose opioids (<20 mg OMEDD); however, the differences in absolute rates are quite low.14
Refer to Metabolism and duration of activity
Additionally, the risk of fatal overdose increases with:15
- slow-release and long-duration opioids
- co-prescription of opioids and benzodiazepines
- sleep-disordered breathing
- reduced renal or hepatic function
- older age
- mental health disorders including SUDs.
In Victoria, 80% of all drug overdoses from 2001 to 2013 involved prescription medications, and pharmaceutical opioids contributed to half of all drug-overdose deaths during that time.3 Fatal overdosing with pharmaceutical opioids is related to dose and duration of action.3,16,17
Annual frequency of overdose deaths involving most frequent contributing individual drugs, Victoria 2009–1618
* Pentobarbitone prescribing to humans is not permitted in Australia, and the drug could be alternatively classified as illegal † Routine post-mortem testing for pregabalin did not commence in Victoria until 2013
Reproduced from the Coroners Court of Victoria. Submission to the Inquiry into Drug Law Reform: Coronial recommendations on drug harm reduction. Melbourne: Coroners Court of Victoria, 2017.
In February 2017, the Coroners Court of Victoria in partnership with Turning Point Alcohol and Drug Centre concluded a study that examined the circumstances in which overdose deaths involving pharmaceutical drugs occur in Victoria. Regarding victims of overdose deaths:18
- 71% had an SUD
- 73% had a diagnosed mental illness
- 49.6% had both a diagnosed mental illness and a documented SUD.
These patients often had a long-established clinical history of mental illness and drug dependence and had in most cases been known to the health system for extended periods of time (ie longer than 10 years).18
This conclusion underpins advice to avoid prescribing opioids to patients with comorbid alcohol or substance use disorders or polydrug use. GPs should consider seeking specialist opinion in the management of these patients. Patients who use two or more psychoactive drugs in combination (particularly benzodiazepines and opioids) and those with a history of substance misuse may be more vulnerable to major harms.