Synthetic opioid may have caused hundreds more deaths than recorded

Deaths caused by a synthetic opioid 500 times more powerful than heroin were likely underestimated by a third, researchers suggest.

Nitazenes are a class of synthetic opioids that are extremely potent and can be produced at low cost. The drugs were first produced as painkillers in the 1950s, but their development was discontinued due to their extreme effects, resulting in a high risk of addiction.

The presence of nitazenes in the unregulated pharmaceutical market has increased rapidly over the past seven years; this has led to UK and international organizations issuing public health warnings about their use.

While the National Crime Agency (NCA) reported 333 deaths linked to nitazenes in 2024, researchers at King’s College London believe the number of deaths is under-reported because concerns have been raised by toxicologists about stability in post-mortem blood samples. This means that nitazenes were likely missed in post-mortem toxicology tests.

Dr D., senior lecturer in pharmacology and toxicology at King’s College London. Caroline Copeland said: “If niacins are degrading in post-mortem blood samples then we are almost certainly undercounting the true number of deaths they cause. This means we are trying to tackle a crisis by using incomplete data.”

“When we don’t measure a problem accurately, we don’t design the right interventions, and the inevitable result is that preventable deaths continue.”

The study was published Monday by researchers at King’s College London. Clinical ToxicologyIt sheds light on the UK’s growing synthetic opioid problem.

Researchers tested samples from mice anesthetized with the drug and found that, on average, only 14 percent of the nitazenine present at the time of the overdose was present when tested under real-world pathology and toxicology sample processing conditions.

Academics then applied modeling to data from the UK’s National Substance Use Mortality Program (NPSUM) to find drug-related deaths were a third (33 per cent) higher in Birmingham in 2023.

Because it usually takes about a month for blood samples to be analyzed by toxicologists, researchers believe a reliable explanation for at least some of these excess deaths may lie in the failure to detect degraded nitracene before toxicology testing is done.

“This research shows that the harm caused by nitazenes is likely to be significantly underestimated. Because these drugs degrade in the blood after death, we may be missing a third of the deaths in which they are involved, meaning public health interventions are designed and funded for only two-thirds of the real problem,” Dr Copeland said.

“Behind this undercount are people dying suddenly from extremely powerful opioids, families left unanswered, and communities facing a growing but largely hidden cost.”

Charity Turning Point said it was organizing testing drives for synthetic opioids, but added that a national drug checking service where people could submit substances for testing to find out whether they contained nitracene could lead to fewer overdoses and deaths.

Nat Travis, head of national service at Turning Point, said: “We would like to see all toxicologists request testing for nitazenes as they are not currently included in standard, routine drug screenings. Toxicology backlogs in London and the UK are also contributing to the significant undercount of deaths related to nitazenes because these substances can degrade in post-mortem blood and potentially conceal up to a third of the deaths in which they are involved.”

Synthetic opioids such as fentanyl, methadone and buprenorphine have been linked to 524 deaths in England since the end of September 2025, according to the Department for Health and Social Care (DHSC).

The government has provided an additional £310 million in public health grants to improve drug and alcohol treatment services and recovery support in England in a bid to reduce drug use.

Naloxone, a fast-acting drug designed to reverse opioid overdoses, is being distributed to a further 32 police forces.

A government spokesman said: “Every death resulting from drug use is a tragedy.

“This government is committed to reducing drug-related deaths and supporting the recovery of more people to live healthier, longer lives. We remain highly alert to emerging drug threats, working closely with health service and police partners to stay one step ahead of criminals targeting our communities.

“Border Force also became the first agency in the world to use specially trained dogs to detect both deadly fentanyl and nitazenes.”