Fentanyl in the US heroin supply: A rapidly changing risk environment.

The supply of heroin into the US has changed with new sourceforms and market strategies. Of particular concern is the rampant and persistent adulteration of heroin with synthetic opioids, most conspicuously the family of fentanyls. Medical consequences including alarming reports of increasing opioid-related overdose, chest wall rigidity syndrome and naloxone resistant overdoses demand urgent public health and policy responses. This Special Section of the International Journal of Drug Policy explores the phenomenon of substituting “traditional” heroin with new less predictable and less culturally established forms and how those forms are perceived and adopted or avoided by those who use them; it maps the consequences and explores structural risk as well as behavioral risk-factors. The research papers and commentaries presented herein discuss the supply-side shock of synthetic opioids that presents multiple overlapping challenges and paradoxes for epidemiological and toxicological surveillance, supply-side intervention, cryptomarkets and public health intervention.