OPINION: Heroin supplies in the US are now commonly adulterated with animal tranquillizer xylazine, a drug which when injected can lead to widespread lesions that cause tissue death – hence the name ‘zombie drug’: with the first reported case of xylazine in a UK drug-user’s death now recorded, King’s College London Pharmaceutical Lecturer Dr Caroline Copeland believes heroin users must be made aware of the additional risks – especially as opioid overdose reversal agent naloxone is not effective against the sedative effects of xylazine.