Study finds drug users may not know which opioid they take

People who inject drugs in Kohtla-Järve often reported taking a different synthetic opioid from the substance found in their urine, a study reported by ERR found. Researchers say the results suggest new synthetic opioids are being sold under the names of substances users already know.

The study, led by Katri Abel-Ollo, who heads the drug field at the National Institute for Health Development and is a researcher, compared participants’ accounts of their drug use with laboratory analyses of urine samples. Abel-Ollo said the rapidly changing market means users may not know what substance they are taking, making an already high-risk activity more dangerous.

The study involved 350 people who inject drugs in Kohtla-Järve. Of those, 112 voluntarily provided urine samples and answered questions about their drug use in the previous seven days. Some 33.9% of those who gave samples reported using a synthetic opioid, naming fentanyl, nitazenes or a substance known on the street as “strong.”

Laboratory tests found cyclorphine in half of the samples from people who reported using fentanyl, nitazenes or “strong.” Overall, cyclorphine was detected in 22 samples, nearly one-fifth of those tested. It was also found in some people who had reported using other substances.

“People usually know the name under which they bought a substance. Laboratory analysis makes it possible to see what actually entered the body,” Abel-Ollo said, adding that combining the two types of information helps researchers understand how the drug market is changing.

Cyclorphine is one of a group of new synthetic opioids known as orphines. The National Institute for Health Development’s annual public health report says orphines were first observed on Estonia’s drug market in 2025. That year, orphines were linked to 10 drug-related deaths.

Synthetic opioids can vary considerably in strength and effect, Abel-Ollo said. If a substance changes but a person continues using a familiar amount, its effects may be much stronger or different than expected, increasing the risk of severe poisoning or overdose.

The study also examined how long cyclorphine remained detectable in urine. When it was detected, an average of 17.1 hours had passed since use. In cases where a person had reported using a synthetic opioid but cyclorphine was no longer detected, an average of 47.6 hours had passed.

Synthetic opioids from the nitazene group began spreading in Estonia in 2019, and their wider circulation was reflected in the number of poisoning deaths in 2022.