Opioid-related emergency department (ED) presentations are selected using the following definition:

1. Unplanned ED presentations to 64 NSW hospitals

2. By persons aged 16 years and older

3. Arriving from 1 July 2011 to 30 June 2021

4. For codeine, fentanyl, oxycodone: where the provisional diagnosis was contained within one of the following four diagnosis groupings (syndromes): overdose/poisoning, acute alcohol problems, illicit drugs or mental health problems. 

    For heroin: then keyword search is applied to all records.

Where the nursing assessment free-text, presenting problem or diagnosis description fields included any of the following terms (noting that the text search was not case-sensitive, and was performed after replacing punctuation with space characters):

•heroin: her(oi|io)n*

•codeine: (cod(ei|ie)ne|panadeine|dolased|mysendol|mersyndol|mersyndal|mersindol)*, (nurofen|nuerofen|neurophen) plus*

•fentanyl: fent*, durogesic*

•oxycodone: oxyco*, oxynorm*, endone*, targin*

Records were excluded if they related to an allergy to the selected substance or where the substance was provided in a therapeutic setting.
Consistency in search method and inclusion criteria allow trends in emergency department data over time to be examined by drug type. Comparisons between different drug types using emergency department data are not meaningful because the following differ across drug types:

The introduction of Activity Based Funding of hospital emergency departments in July 2012 led to a change in the diagnoses available for selection by clinicians and an apparent increase in completeness of diagnoses relating to mental illness. This may have affected these statistics.