Purity and adulterants in street heroin in Denmark from 2006 to 2024

An opioid epidemic has hit many countries across the world in recent years. High-potency opioids, sometimes mixed with heroin or other traditional opioids, have contributed substantially to this epidemic. In Europe, the amount of heroin seized has declined since 2011, and the population of treatment seekers is aging. This study aimed to elucidate the number of heroin seizures pr. year according to statistics reported by the Danish police. Furthermore, we used samples from the "Drugs at street-level in Denmark" (DSLD) project to assess trends in purity and adulterants, including high potency opioids such as fentanyls and nitazenes, or other new psychoactive substances (NPS) in heroin seized at the street level in Denmark. The total number of heroin seizures pr. year declined from 1499 in 2006-207 in 2024. The DSLD project included 676 samples, of which 415 were heroin base, 256 were heroin chloride, and five were unclassified. The median (interquartile range) seizure was 0.29 (0.15 - 0.56) grams, and the median purity was 22 (14 - 35) %. The median purity of heroin base and heroin chloride was 18 (12-25) % and 35 (24.5-46.5) %, respectively, and varied between regions. The purity of heroin chloride decreased over the years, while the purity of heroin base increased slightly. The most common adulterants were caffeine (87.8 %), and acetaminophen (71.4 %), often co-occurring (70.6 %). No fentanyls, nitazenes, or other NPS, were detected. These findings suggest that heroin is gradually becoming less prominent within the Danish illicit drug market.