Emerging Synthetic Fentanyl Analogs

Abstract

Hundreds of synthetic substances have been introduced into the illicit drug market over the last ten years, but none of these drugs has had as poisonous a consequence as the emergence of the synthetic fentanyl analogs. Initially, pharmaceutical grade or illicit fentanyl was mixed with heroin, allegedly to boost the potency of the heroin. Then, the amounts of fentanyl spiked gradually increased until the proportion of fentanyl was greater than the proportion of heroin. Ultimately, many overdose cases began consisting of only fentanyl. The emergence of numerous synthetic fentanyl analogs, including acetylfentanyl, butyrylfentanyl, acrylfentanyl, furanylfentanyl and β-hydroxythiofentanyl, which are manufactured in China, were made available to the illicit drug traffickers over the Internet. In July of 2016, the most potent commercially available opioid, carfentanil, started appearing in illicit drug submissions and medical examiner death investigation cases in Northeast Ohio. Postmortem femoral blood carfentanil concentrations are in the picogram per milliliter (pg/mL) range, which is extremely low, and tests the limits of detection for most analytical forensic toxicology laboratories. The interpretation of these low carfentanil blood concentrations in antemortem and postmortem specimens is made difficult due to the overlap in the concentrations between these specimen types. The presence of these powerful synthetic fentanyl analogs presents a challenge to forensic toxicology laboratories preparing to analyze for these substances.

Keywords: 3-methylfentanyl; Carfentanil; Fentanyl analogs; Forensic pathology; Synthetic opioids.

Figure 1

Structures of some fentanyl analogs.