A study published by the European Union Drugs Agency (EUDA) has found an overall increase in the levels of ketamine and cocaine in wastewater and decreases in traces of ecstasy in cities all over Europe.
Ketamine levels in Dublin increased by over 40%, cannabis was up over 8%, but the levels of cocaine and ecstasy in wastewater were each down by over 20%.
The study analysed daily wastewater samples in the catchment areas of wastewater treatment plants over a one-week period between March and May 2025.
The analysis in Dublin was carried out on wastewater from the Ringsend treatment plant in Dublin.
Wastewater samples from a population of 72 million people across 115 European cities in 25 countries were analysed for traces of six drugs, stimulant drugs amphetamine, cocaine, methamphetamine, MDMA, ketamine and cannabis.
Overall ketamine loads in wastewater were found to have increased by 41% from 2024 to 2025, while cocaine increased by nearly 22%.
The levels for MDMA, commonly known as ecstasy dropped by 16%, while diverging patterns were established for cannabis, amphetamine and methamphetamine.
More than 75% of the 115 cities surveyed showed higher residues of cocaine and MDMA at the weekends from Friday to Monday, while almost half showed higher loads of ketamine.
In contrast, residues of amphetamine, methamphetamine and cannabis were distributed more evenly throughout the week.
Analysis of wastewater from the treatment plant at Ringsend also showed an increase in ketamine levels by over 42% (42.2%).
Cannabis levels increased by over 8% (8.5%) while cocaine levels dropped over the year by over 21% (21.7%).
Cocaine levels were found to be highest in Dublin on Fridays and Mondays.
The levels of ecstasy (MDMA) in Dublin's wastewater was also down by over 23% (23.5%) over the year and there were also reductions in recorded levels of amphetamine and metamphetamine.
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Mostly younger people using ketamine - analyst
EUDA scientific analyst João Matias said the agency was already aware that ketamine use was going up across Europe; he said there were several possible reasons for this including a drop in the use of MDMA or ecstasy among young people
"It seems ketamine in recreational settings is more available now in European markets; I think this is linked to the effects the drug gives to those who decide to use it."
Mr Matias said it was mostly younger people in the 15-24 age cohort who are using ketamine.
He said he hoped public health officials would take all the evidence and data collated by EUDA to have better interventions for prevention and harm reduction.
Consultant Urologist Dr Eabhann O'Connor said ketamine use can cause serious health problems and that she has seen an increase in people requiring medical attention.
She said ketamine is a "pretty unique drug" compared to others because of what it can do to a person's bladder.
"Its metabolites, or what it's broken down into, can travel directly to the bladder," she said.
Dr O'Connor, who runs a clinic in St Vincent's Hospital in Dublin, said bladder disease caused by ketamine use can range from needing to go to the toilet more frequently but can progress to kidney failure and to patients losing their bladder.
She said it was important to talk about ketamine, and for better public health messaging around its use..."targetting people in secondary schools, nightclubs and festivals - for them to be aware that the effect of ketamine on the bladder is related to the frequency of use and the dose", she added.
