Following series of synthetic cannabinoid and synthetic cathinone derivatives, the illicit drug market has begun to see increased incidence of synthetic opioids including fentanyl and its derivatives, and other chemically unrelated opioid agonists including AH-7921 and MT-45. Among the most frequently encountered compounds in postmortem casework have been furanyl fentanyl (N-(1-(2-phenylethyl)-4-piperidinyl)-N-phenylfuran-2-carboxamide, Fu-F) and U-47700 (trans-3,4-dichloro-N-(2-(dimethylamino)cyclohexyl)-N-methylbenzamide). Both drugs have been reported to be present in the heroin supply and to be gaining popularity among recreational opioid users, but were initially developed by pharmaceutical companies in the 1970s as candidates for development as potential analgesic therapeutic agents. A method was developed and validated for the analysis of U-47700, U-50488 and furanyl fentanyl in blood specimens. A total of 20 postmortem cases, initially believed to be heroin or other opioid-related drug overdoses, were submitted for quantitative analysis. The analytical range for U-47770 and U-50488 was 1-500 and 1-100 ng/mL for furanyl fentanyl. The limit of detection was 0.5 ng/mL for all compounds. Within the scope of the method, U-47700 was the only confirmed drug in 11 of the cases, 5 cases were confirmed for both U-47700 and furanyl fentanyl, and 3 cases were confirmed only for furanyl fentanyl. The mean and median blood concentrations for U-47700 were 253 ng/mL (±150) and 247 ng/mL, respectively, range 17-490 ng/mL. The mean and median blood concentrations for furanyl fentanyl were 26 ng/mL (±28) and 12.9 ng/mL, respectively, range 2.5-76 ng/mL. Given the widespread geographical distribution and increase in prevalence in postmortem casework, toxicology testing should be expanded to include testing for "designer opioids" in cases with histories consistent with opioid overdose but with no traditional opioids present or insufficient quantities to account for death.

The synthetic opioid landscape continues to change as non-fentanyl-related substances appear in forensic toxicology casework. Among the newest synthetic opioids to emerge is isotonitazene, an analogue of a benzimidazole class of analgesic compounds. Isotonitazene is an active and potent synthetic opioid, but the extent to which this compound is causing toxicity among drug users was previously unknown. This report describes the confirmation and quantitation of isotonitazene in blood, urine and vitreous fluid through standard addition, as well as in vivo metabolic profile determination in drug users. Quantitative analysis was performed using liquid chromatography tandem mass spectrometry (LC–MS/MS), and metabolite discovery was performed using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). In total, 18 cases were confirmed positive for isotonitazene, nine of which were previously negative for any opioid. The average isotonitazene concentration in blood was 2.2 ± 2.1 ng/mL (median 1.75 ng/mL, range 0.4–9.5 ng/mL), and the average isotonitazene concentration in urine was 2.4 ± 1.4 ng/mL (median 2.7 ng/mL, range 0.6–4.0 ng/mL). The lowest concentration of isotonitazene in blood was 0.4 ng/mL (two cases) with no other opioids present; findings in death investigations. Four metabolites of isotonitazene were detected in vivo. N- and O-dealkylation products were determined to be the most prominent urinary biomarkers, while 5-amino-isotonitazene was identified in most blood samples. The prevalence and popularity of isotonitazene continue to increase in the United States in early 2020. Toxicologists, medical examiners and coroners should be aware of novel opioids outside the standard scope of testing, especially in medicolegal death investigations. Forensic scientists should add isotonitazene to testing procedures, and public health officials should counsel about potent new drugs and the dangers of opioid use.

Novel psychoactive substances (NPS) represent significant analytical and interpretive challenges to forensic and clinical toxicologists. Timely access to case reports and reports of adverse incidents of impairment or toxicity is imperative to clinical diagnosis and treatment, as well as to interpretation of forensic results. Delays in identifying the presence of a novel intoxicating agent have significant consequences for public health and public safety. Adverse effects of intoxications with novel cannabinoids, stimulants, hallucinogens, benzodiazepines and opioids spanning January 2013 through December 2016 as reported in emergency departments, death investigations, impaired driving cases and other forensic contexts are the subject of this review. Discussion of the chemistry, pharmacology and adverse events associated with novel drug classes is summarized and described within. Adverse effects or symptoms associated with ingestion of more than 45 NPS have been abstracted and summarized in tables, including demographics, case history, clinical or behavioral symptoms, autopsy findings and drug confirmations with quantitative results when provided. Based on these findings and gaps in the available data, we provide recommendations for future toxicological testing of these evolving substances. These include development and management of a national monitoring program to provide real-time clinical and toxicological data, confirmed analytically, on emerging drugs and their known toxidromes and side effect profiles. Increased efforts should be made to analytically confirm the agents responsible for clinical intoxications involving adverse events in emergency department admissions or hospitalizations. Evidence-based community preparedness among analytical laboratories gained through active communication and sharing of toxicological findings and trends in NPS is imperative to assist in enabling early detection of new drugs in forensic and clinical populations.

Methoxyacetylfentanyl and cyclopropylfentanyl are two of the newest illicit opioids that are infiltrating the heroin market. Methoxyacetylfentanyl and cyclopropylfentanyl were reported by the Drug Enforcement Administration (DEA) in their third quarter report of 2017 to have been chemically identified seven and five times, respectively, from drug evidence analyzed by the DEA's lab system; Q3 was the first time cyclopropylfentanyl was identified by the DEA's lab system, while methoxyacetylfentanyl was reported one time in Q2 2017. A method was developed using liquid chromatography tandem mass spectrometry for the quantitation of fentanyl, norfentanyl and 17 fentanyl analogs: furanylfentanyl, butyrylfentanyl, despropionylfentanyl (4-ANPP), methoxyacetylfentanyl, tetrahydrofuran fentanyl, fluoro-isobutyrylfentanyl, acrylfentanyl, para-fluorofentanyl, ortho-fluorofentanyl, carfentanil, beta-methylfentanyl, isobutyrylfentanyl, para-methylfentanyl, cyclopentylfentanyl, cyclopropylfentanyl, beta-hydroxyfentanyl and alpha-methylfentanyl. The calibration range for all compounds was 0.1-100 ng/mL. Blood samples from 42 postmortem cases involving cyclopropylfentanyl and methoxyacetylfentanyl from Florida, Illinois, Michigan and Tennessee were submitted for toxicological analysis. The mean and median concentration for the cases testing positive for cyclopropylfentanyl (n = 32) was 15.3 (±11.9) ng/mL and 12.3 ng/mL, respectively, with a range of 1.4-43.3 ng/mL. The mean (±SD) and median concentrations for the 11 cases quantitatively confirmed (3 cases were below the limit of quantitation) for methoxyacetylfentanyl was 17.7 (±11.4) ng/mL and 15.1 ng/mL respectively, with a range of 0.21-39.9 ng/mL. These novel illicit substances typically are outside the scope of routine drug testing by hospitals and toxicology laboratories or below the sensitivity levels for the detection of these substances in biological specimens. These compounds have not previously been studied in humans; therefore, it is significant to be able to associate the pharmacological effects derived from case reports to the quantitative values found in the postmortem specimens.

MT-45 (1-cyclohexyl-4-(1,2-diphenylethyl)piperazine) is just one of the many novel psychoactive substances (NPS) to have reached the recreational drug market in the twenty-first century; it is however, one of the first designer opioids to achieve some degree of popularity, in a market currently dominated by synthetic cannabinoids and designer stimulants. A single fatality involving MT-45 and etizolam is described. A method for the quantitation of MT-45 in whole blood using liquid chromatography-tandem mass spectrometry was developed and validated. The linear range was determined to be 1.0-100 ng/mL with a detection limit of 1.0 ng/mL, and the method met the requirements for acceptable linearity, precision and accuracy. After analyzing the sample on dilution and by standard addition, the concentration of MT-45 in the decedent's blood was determined to be 520 ng/mL, consistent with other concentrations of MT-45 reported in drug-related fatalities. Etizolam was present at a concentration of 35 ng/mL. This case illustrates the importance of considering non-traditional drugs in unexplained apparent drug-related deaths.

Metonitazene is considered a new psychoactive substance (NPS) and emerging potent synthetic opioid, causing increased public health concern beginning in 2020. Metonitazene joins a growing list of new synthetic opioids (NSOs) contributing to deaths among people who use drugs in the United States and other parts of the world. Metonitazene (a 2‐benzylbenzimidazole analogue) first appeared in mid‐2020 in the recreational drug supply and subsequently began proliferating in death investigation casework towards the end of 2020. Screening and metabolite discovery were performed by liquid chromatography quadrupole time‐of‐flight mass spectrometry. Quantitative confirmation was performed by liquid chromatography tandem quadrupole mass spectrometry. Metonitazene was confirmed in 20 authentic forensic postmortem cases with an average concentration in blood at 6.3 ± 7.5 ng/ml (median: 3.8 ng/ml, range: 0.5–33 ng/ml, n = 18) and in urine at 15 ± 13 ng/ml (median: 11 ng/ml, range: 0.6–46 ng/ml, n = 14). Metonitazene was the only opioid identified in 30% of cases but was also found in combination with fentanyl (55%) and NPS benzodiazepines, opioids, and hallucinogens (45%). Medical examiners included metonitazene as a drug responsible for the cause of death, and the manner of death was always ruled to be an accident. The metabolism of metonitazene was found to be similar to that of isotonitazene, a closely related analogue. Toxicology laboratories and death investigators should ensure that metonitazene is included in forensic testing protocols, all while remaining vigilant for subsequent NSOs to emerge.

The recreational use of opioid drugs is a global threat to public health and safety. In particular, an epidemic of opioid overdose fatalities is being driven by illicitly manufactured fentanyl, while novel synthetic opioids (NSOs) are appearing on recreational drug markets as standalone products, adulterants in heroin, or ingredients in counterfeit drug preparations. Trans-3,4-dichloro-N-[2-(dimethylamino)cyclohexyl]-N-methylbenzamide (U-47700) is a prime example of a non-fentanyl NSO that is associated with numerous intoxications and fatalities. Here, we review the medicinal chemistry, preclinical pharmacology, clandestine availability, methods for detection, and forensic toxicology of U-47700 and its analogs. An up-to-date summary of the human cases involving U-47700 intoxication and death are described. The evidence demonstrates that U-47700 is a potent μ-opioid receptor agonist, which poses a serious risk for overdosing and death. However, most analogs of U-47700 appear to be less potent and have been detected infrequently in forensic specimens. U-47700 represents a classic example of how chemical entities from the medicinal chemistry or patent literature can be diverted for use in recreational drug markets. Lessons learned from the experiences with U-47700 can inform scientists, clinicians, and policymakers who are involved with responding to the spread and impact of NSOs.

Recently, the number of adverse events, including death, involving novel opioids has continued to increase, providing additional and sustained challenges for forensic and medical communities. Identification of emerging novel opioids can be challenging, compounded by detection windows and unknown metabolic profiles. In this study, human liver microsomes were used for the generation of in vitro metabolic profiles of U-47700 and U-49900. Generated metabolites were analyzed via a SCIEX TripleTOF® 5600+ quadrupole time-of-flight mass spectrometer and resulting data files were processing using MetabolitePilot™. Characterized metabolites were verified in vivo by analysis of authentic human urine specimens collected after analytically confirmed cases of overdose involving U-47700 or U-49900. In total, four metabolites were identified and present in urine specimens for