Dr Adam Holland, one of the study's co-authors said: "The emergence of xylazine in the UK drug market, as well as the proliferation of potent synthetic substances including nitazenes and benzodiazepine analogues is extremely concerning. As levels of adulteration increase and drug-related deaths mount it becomes even more clear that our punitive drug laws are not reducing harm.  

"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."