Animal tranquilliser found in cannabis vapes and illicit sedatives in UK

Xylazine has been found in counterfeit prescription drugs such as codeine, alprazolam and diazepam tablets and vapes containing THC, the psychoactive ingredient in cannabis. Photograph: Robert F Bukaty/AP

People buying cannabis vapes and illicit sedatives to treat pain, anxiety and insomnia risk unknowingly consuming a powerful animal tranquilliser that can cause skin ulcers and overdoses.

Xylazine has been prevalent in the US for several years, where it is commonly found mixed with strong opioids, such as heroin or fentanyl, and has caused thousands of deaths.

Research from King’s College London has found that its presence has been steadily growing in the UK, causing multiple deaths since 2022, when the first fatality was identified.

Unlike in the US, in the UK xylazine has been found in counterfeit prescription drugs such as codeine, alprazolam (Xanax) and diazepam (Valium) tablets and vapes containing THC, the psychoactive ingredient in cannabis.

Dr Caroline Copeland, senior author of the study, said: “This is cause for alarm as a much wider population of people who use drugs beyond heroin users will be exposed to its harms.

“We also know that most people who buy heroin will not intend to buy xylazine and this combination increases the risk of overdose. Xylazine was designated an ‘emerging threat’ to the United States and this public health threat is a growing concern for the UK.”

The findings, published in the Addiction journal, drew on evidence from all toxicology laboratories in the UK. The drug was found in 16 people, 11 of whom died.

In nine of the 11 confirmed deaths xylazine was found in combination with a strong opioid. The lack of this combination in the other two cases suggests xylazine was potentially consumed in an illicit sedative or vape.

Copeland said the total number of deaths is likely higher, since xylazine does not stay in the body for long. Since August 2023, the last death covered by the research, “we’ve had several more deaths so it is only continuing and increasing”, she said.

Xylazine is a non-opioid sedative, painkiller and muscle relaxant used in veterinary medicine, which can dangerously lower breathing and heart rate. It is known as tranq when cut with heroin and fentanyl. If injected directly into the user’s bloodstream it can form large open skin ulcers, which if infected may result in limb amputation.

Copeland recommended measures to avoid an epidemic of xylazine use, which resulted in a 20 fold increase in deaths within three years in the US, including requiring pathologists and coroners to request toxicology testing for xylazine to understand the true prevalence of the drug.

Xylazine’s emergence follows the spread of nitazenes, which are synthetic and extremely powerful drugs implicated in a spate of recent deaths of heroin users.

Co-author Dr Adam Holland, a co-chair of the drugs special interest group at the University of Bristol, said the increase in drug adulteration and deaths shows that punitive drug laws are failing. He added: “We need to expand the range of harm reduction interventions available for people who use drugs, including drug checking and overdose prevention centres, to give them the opportunities they need to stay safe.”

A government spokesperson said: “We are aware of the threat from xylazine and are determined to protect people from the threat posed by this drug and other illicit synthetic drugs.

“We will not hesitate to act to keep the public safe. Following advice from the Advisory Council on the Misuse of Drugs, we intend to make xylazine a class C drug meaning anyone supplying this substance will face up to 14 years in prison, a fine or both.”