Media release

From: University of South Australia

Searching for a lethal needle in a haystack: traces of highly potent synthetic opioids found in used syringes

A class of synthetic opioids that are up to 1000 times more potent than morphine have been found in used syringes across metropolitan Adelaide, sparking fears of a wave of overdoses that could be lethal.

In the first study of its kind in South Australia, University of South Australia researchers have detected traces of nitazene in samples of discarded injecting equipment, plastic bags, vials and filters from public disposal bins at local needle and syringe program sites.

Their findings are published today (Friday 1 August) in the Drug & Alcohol Review.

Using highly sensitive chemical analysis, researchers identified nitazenes in 5% of 300 samples, mainly in combination with heroin and mostly found in syringes.

Nitazenes led to 32 overdose deaths in Australia between 2020 and 2024, with 84% of patients unaware the synthetic opioid was present in the drug they consumed. It is increasingly hidden in illicit drugs such as fentanyl and heroin, posing extreme overdose risks, often with fatal consequences.

“Nitazenes are among the most potent synthetic opioids in circulation today, some stronger than fentanyl, which is 50 times more potent than heroin,” according to lead researcher UniSA Associate Professor Cobus Gerber.

“These substances can be lethal in tiny quantities and are often mixed with other drugs, making them incredibly difficult to detect and monitor through traditional means,” he says.

Several different nitazenes were identified, some of them combined with the non-opioid veterinary sedative xylazine, which is not approved for human use.

“This is particularly alarming,” says Assoc Prof Gerber, “as xylazine has been linked to severe adverse effects, including necrotic skin lesions, prolonged sedation and depression.

“Finding xylazine alongside nitazenes in the same samples is a worrying sign because it mirrors what we are seeing overseas, especially in the United States, where these drug combinations are contributing to a wave of overdose deaths and complex clinical presentations.”

Less than one in five nitazene-related emergency cases in Australia involved people who knowingly took the drug, with most people mistakenly believing they consumed heroin, methamphetamine or other familiar substances.

“Accidental exposure is a key risk,” says co-author UniSA researcher Dr Emma Keller.

“When drugs are contaminated with nitazenes, the margin for error narrows dramatically. Standard doses can become fatal, especially for people who don’t know what their product contains or who don’t carry naxolone, a medication that can rapidly reverse the effects of an opioid overdose.”

The detection of these substances in South Australia comes amid growing calls for expanded drug-checking services, including the use of nitazene-specific drug strips and public health alerts.

Associate Prof Gerber says that chemical testing of used drug paraphernalia is a non-invasive, effective way to identify emerging threats in the drug supply.

“This kind of data can trigger rapid alerts to health agencies, treatment services and peer networks, allowing people who use drugs to make more informed choices.”

Wastewater analysis is also used to detect illicit drugs in the community, but due to the sporadic nature of drug use, other monitoring approaches like chemical testing are necessary.

Drug and Alcohol Services South Australia, who co-authored the study, has shared the findings with community advisory groups, healthcare providers and the state’s early warning system network.