The UK government on Wednesday banned the flesh-rotting so-called zombie drug xylazine as it tries to tackle deaths from narcotics and crack down on criminal gangs.
The high-strength animal sedative, also known as "tranq", often leaves long-term users in an unresponsive state and with non-healing skin lesions.
It has increasingly been used in combination with opioids such as heroin, with traces found in cannabis vapes as well, according to the UK Home Office.
The UK government in September announced plans to ban xylazine and 21 other dangerous substances, the legislation for which came into force on Wednesday.
The other drugs banned include new variations of nitazenes -- highly addictive synthetic opioids that can be hundreds of times stronger than heroin and easily lead to overdoses.
There have been at least 400 drug-related deaths linked to nitazenes in the UK since June 2023, according to the government,
"We are dedicated to driving down drug misuse and harms through prevention and treatment while acting quickly to stop the criminals peddling these harmful substances," said policing minister Diana Johnson.
The UK's Misuse of Drugs Act sets out three separate categories for "controlled drugs", with Class A drugs deemed the most dangerous and the most harshly punished.
Xylazine is categorised as Class C, meaning unlawful possession can carry a sentence of up to two years in prison. Anyone convicted of supplying it face up to 14 years in jail.
Researchers at King's College, London have said tranq is "widespread" in the UK's illicit drug market.
The United States is also grappling with a surge in use of the dangerous drug.
Xylazine-involved overdose deaths there rose 30-fold between 2018 and 2021.