Systematic review of the clinical consequences of butyrfentanyl and corresponding analogues

Butyrfentanyl and its analogues are being increasingly used throughout the United States and Europe. Currently, lethal cases are emerging across the United States, England, and Europe without any end in sight. We therefore performed a systematic review of existing case reports on the literature of butyrfentanyl and similar analogs. We searched PubMed and Embase for articles (up until September 2018) using terms such as "butyrfentanyl" or "butyrylfentanyl." In total, our search found 271 articles and identified 10 for inclusion in this review. A total of 33 cases were found with 61% of those being fatal. The most common route of administration was intravenous, but other routes of administration were readily used such as oral, intranasal, and inhalation. Most cases reported use of concomitant licit and illicit pharmacological agents. The toxidrome was consistent with other opioid overdoses, and naloxone was successfully used in nine of 10 patients. We encourage toxicology screenings of novel fentanyl analogs such as butyrfentanyl or 4-fluorobutyrfentanyl when an opioid overdose of unknown nature presents.