Jonathan P. Caulkins

Background and aims Synthetic opioids, mostly illegally manufactured fentanyl (IMF), were mentioned in 60% of United States (US) drug overdose deaths in 2020, with dramatic variation across states that mirrors variation in IMF supply. However, little is known about IMF markets in the United States and how they are changing. Researchers have previously used data from undercover cocaine, heroin, and methamphetamine purchases and seizures to examine how their use and related harms respond to changes in price and availability. This analysis used US Drug Enforcement Administration (DEA) data to address two questions: (i) “To what extent does IMF supply vary over time and geography?” and (ii) “What has happened to the purity‐adjusted price of IMF?” Methods We developed descriptive statistics and visualizations using data from 66 713 observations mentioning IMF and/or heroin from the DEA's System to Retrieve Information from Drug Evidence (STRIDE; now STARLIMS) from 2013 to 2021. Price regressions were estimated with city‐level fixed effects examining IMF‐only powder observations with purity and price information at the low‐to‐medium wholesale level (>1 g to ≤100 g; n = 964). Results From 2013 to 2021, the share of heroin and/or IMF observations mentioning IMF grew from near zero to more than two‐thirds. The share of heroin observations also containing IMF grew from <1% to ~40%. There is important geographic variation: in California, most IMF seizures involved counterfeit tablets, whereas New York and Massachusetts largely involved powder formulation. The median price per pure gram of IMF powder sold at the >10 to ≤100 g level fell by more than 50% from 2016 to 2021; regression analyses suggested an average annual decline of 17% ( P < 0.001). However, this price decline appears to have been driven by observations from the Northeast. Conclusions Since 2013, the illegally manufactured fentanyl problem in the United States has become more deadly and more diverse.