The drug is used by medical practitioners and veterinarians as an anaesthetic and for pain management, but it is commonly abused for its hallucinogenic and dissociative effects.
Melbourne had the highest estimated average capital city levels of ketamine and Victoria the highest average regional levels.
The wastewater testing and data collection creates a comprehensive picture of Australia's drug markets and habits, covering nicotine and alcohol; the stimulants methylamphetamine, amphetamine, cocaine, MDMA and MDA; the opioids oxycodone, fentanyl and heroin; and cannabis and ketamine.
The drug habits of Australians are laid bare by regular wastewater testing and analysis. (Paul Miller/AAP PHOTOS)
Many Australian illicit drug markets are supplied by serious and organised crime groups, with no regard for laws or the harm their illegal trade causes, the commission's chief executive Heather Cook said.
"These harms may include negative impacts and consequences on the physical and mental health of users and their families, related acts of violence including serious assaults and murder, property crime and dangerous traffic offences," she said.
"Australia continues to be exploited by organised crime, costing the nation up to $60 billion each year, of which $16.5 billion is the result of illicit drug activity."
Despite large seizures during the latest reporting period, organised crime networks continued to fuel Australia's demand for illicit substances.
Cannabis is the most consumed illicit drug by a large margin and regional consumption remains around double the average capital city consumption.
Cannabis is still the most popular illicit substance among Australians, particularly in the regions. (Darren England/AAP PHOTOS)
The data reveals that, despite a decrease in national cocaine consumption since December 2023, consumption remains higher than pre-COVID-19 pandemic levels, signalling a possible longer-term expansion of the market.
Sydney had the highest estimated average capital city consumption of cocaine, while Queensland had the highest average regional consumption.
Methylamphetamine consumption is above long-term average levels, but not quite to the levels prior to COVID-19.
Adelaide had the highest estimated average capital city consumption of methylamphetamine, while WA had the highest average regional consumption.
The April 2024 data collection covered around 56 per cent of Australia's population – about 14.2 million Australians.
The use of cocaine, heroin, fentanyl and ketamine had higher average consumption in capital cities than regional areas, while alcohol, nicotine, oxycodone, methylamphetamine, MDMA and cannabis had higher average usage in the regions compared to the capitals.
Heroin, cocaine, fentanyl and ketamine use was greater in capital cities than in the regions. (Dean Lewins/AAP PHOTOS)
The data also highlighted differences between the Australian drug market and those in North America. While US markets are experiencing an opioid crisis, there was record low regional consumption of oxycodone and fentanyl in Australia in April 2024.
Alcohol and nicotine were the highest consumed drugs in all states and territories in April 2024.
Nationally, consumption of nicotine fell between December 2023 to April 2024.
The amounts of alcohol consumed has been dropping in some states and territories, and nationally, since 2022.
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