REVIEW ARTICLE Furanylfentanyl: another fentanyl analogue, another hazard for public health Nektaria Misailidi 1 • Ioannis Papoutsis 1 • Panagiota Nikolaou 1 • Maria Katselou 1 • Chara Spiliopoulou 1 • Sotiris Athanaselis 1 Received: 11 May 2017 / Accepted: 27 May 2017 Ó Japanese Association of Forensic Toxicology and Springer Japan 2017 Abstract The fentanyls are a family of drugs that have caused hundreds of deaths in Europe and the United States. They first appeared in the United States in the late 1970s; they were sold as heroin to unsuspecting users. Furanylfentanyl is a potent synthetic drug, an analogue of fentanyl that belongs to the above family. It has no proven medical use, but it is abused throughout the world for its opioid-like effects. The drug is mainly manufactured in China and is distributed worldwide. It is used mainly intranasally, but other routes of administration have also been reported. Furanylfentanyl has been involved in many intoxication cases, fatal or not, and many seizures of the drug have been recorded. The aim of this review is to summarize all the available information on furanylfen- tanyl, concerning its chemistry, synthesis, prevalence, metabolism, pharmacology, and toxicology, as well as its legal status. Analytical methods for the determination of furanylfentanyl in biological specimens are presented. Intoxications and lethal cases published in the scientific literature or reported on the web are also reviewed. Keywords Furanylfentanyl Á New psychoactive substance Á Synthetic opioid Á Pharmacology Á Toxicology Á Legal status Introduction New psychoactive substances (NPS) are a group of drugs that have been designed in order to mimic traditional illicit drugs such as cannabinoids, opioids, cocaine, amphetami- nes, and LSD, while at the same time they outsmart the drug laws. These potent and potentially harmful substances are continuously introduced on the recreational drug mar- kets by names such as ‘‘designer drugs’’, ‘‘legal highs’’, ‘‘herbal highs’’ and ‘‘bath salts’’, and they are sold as ‘‘research chemicals’’ or ‘‘laboratory reagents’’. As the trade and use of these synthetic drugs continue to increase, serious harms for public health, such as non-fatal intoxi- cations and deaths, are reported. Among NPS, synthetic opioids are of special concern [1–3]. Opioids are drugs that have effects similar to mor- phine’s. They are used in medicine mainly as analgesics for relief from acute and chronic pain, in the treatment of cancer patients, and postoperatively. Fentanyl is a synthetic opioid, which is about 300 times more potent than mor- phine; therefore, it is used in very low dosages [4]. Its structure allows the manufacturers to compose various analogues of it with similar analgesic activities and effects. Hence, 1400 fentanyl analogues have been synthesized, only 200 of which have been studied pharmacologically. Since 1979 various analogues of fentanyl have been sold on the streets and have been responsible for many overdose deaths [3, 5–9]. During the last 5 years, more than 12 of these analogues have entered the illegal drug market. Although all of such analogues have opioid-like effects and can relieve acute pain, only three of them (remifentanil, alfentanil, and sufentanil) have been used in clinical practice [3]. Non-pharmaceutical fentanyl analogues, such as furanylfentanyl, are often sold to users who sometimes believe that they are using heroin, oxycodone, or other & Panagiota Nikolaou pan_nik@hotmail.com 1 Department of Forensic Medicine and Toxicology, Faculty of Medicine, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece 123 Forensic Toxicol DOI 10.1007/s11419-017-0371-z