An Australia-wide study led by researchers at Adelaide University has found ketamine consumption is increasing across the country.
The study analysed wastewater samples collected between December 2020 and April 2025. Daily influent wastewater samples were collected from treatment plants across capital city and regional sites in all states and territories, covering on average 53 per cent of the total population.
“We found that ketamine mass loads increased across Australia from 2022 to 2025, particularly in sites with higher socioeconomic status,” said Professor Cobus Gerber from Adelaide University’s School of Pharmacy and Biomedical Sciences.
“While our initial findings were largely consistent with expected prescribed use of ketamine, patterns started emerging of substantially elevated excretion on weekends, suggesting an increase in recreational, or non-medical use of the substance.”
Published in Environmental Advances, the study found measured excreted loads fluctuated throughout 2022 reaching a low of about 1.6 mg/day/1000 people, before rising by the end of 2025 to 5.8 mg/day/1000 people.
“The study shows that social advantage and use in or near city locations appear to correlate most strongly with recreational ketamine use,” Professor Gerber said.
“This is clearly an area of concern considering the harm potential of ketamine – long-term health effects include cognitive impairment and cardiovascular effects, but deaths due to ketamine overdose have been on the rise internationally, clearly a more immediate concern when users dabble.”
Ketamine is a pharmaceutical drug used as an anaesthetic, and to treat severe pain and depression due to its dissociative effects. Interest in ketamine and MDMA for the treatment of depression and post-traumatic stress disorder may influence some people to use these drugs non-medically.
“The drug is often consumed alongside other illicit substances to heighten feelings of euphoria and dissociation, with increased online mentions of ‘kitty flipping’, which refers to the combined party use of MDMA (ecstasy) and ketamine,” Professor Gerber said.
The findings align with national data, where the latest National Drug Strategy Household Survey showed non-medical use of ketamine is increasing, with the proportion of people who have ever used ketamine rising from 1.9 per cent in 2016 to 4.3 per cent in 2023.
Professor Gerber said wastewater monitoring measures actual consumption of substances and can reveal patterns of drug use in locations where little other information exists.
“Because samples are anonymous and cover large populations, wastewater epidemiology fills an important gap left by surveys and self-reported data,” Professor Gerber said.
“The method is non-invasive and not stigmatising. No other resource has the population coverage of wastewater monitoring in our country.”
Professor Gerber said the study provides important insight into where resources and harm reduction messaging may be most needed.
The research team recommends future research into behavioural drivers of drug use, including the context in which substances are used, combinations with other drugs, and the origin of non-medical ketamine circulating in the community.
This work is supported by the Australian Criminal Intelligence Commission, Preventative Health SA, and conducted in partnership with the Queensland Alliance for Environmental Health Sciences.
