Comparing fatal cases involving U-47700

Synthetic opioids: a review and clinical update

The term 'opioids' refers to both the natural compounds ('opiates') which are extracted from the opium poppy plant (Papaver somniferum) and their semi-synthetic and synthetic derivatives. They all possess relatively similar biochemical profiles and interact with the opioid receptors within the human body to produce a wide range of physiological effects. They have historically been used for medicinal purposes, their analgesic and sedative effects, and in the management of chronic and severe pain. They have also been used for non-medicinal and recreational purposes to produce feelings of relaxation, euphoria and well-being. Over the last decade, the emergence of an illegal market in new synthetic opioids has become a major global public health issue, associated with a substantial increase in unintentional overdoses and drug-related deaths. Synthetic opioids include fentanyl, its analogues and emerging non-fentanyl opioids. Their popularity relates to changes in criminal markets, pricing, potency, availability compared to classic opioids, ease of transport and use, rapid effect and lack of detection by conventional testing technologies. This article expands on our previous review on new psychoactive substances. We now provide a more in-depth review on synthetic opioids and explore the current challenges faced by people who use drugs, healthcare professionals, and global public health systems.

Blood concentrations of new synthetic opioids

PURPOSE

Over the last decade, there has been a significant growth in the market and number of new psychoactive substances (NPS). One of the NPS groups that has grown rapidly in recent years, bringing a new set of problems, consists of new synthetic opioids. The extreme potency of these compounds poses a high risk of acute poisoning, as an overdose can cause respiratory depression. Most of the information regarding human pharmacokinetics of new opioids is based on toxicological case reports and the data on concentrations of new opioids in human blood are scarce. The interpretation of results usually requires a comparison to previously published cases; therefore, a referenced compilation of previously published concentration data would be useful.

METHODS

The data were collected by searching the PubMed and Scopus databases and by using the Google search engine. All the available data from articles and reports that measured new opioid concentrations in plasma, serum, or whole blood were included in the data analysis.

RESULTS

The presented tables list the observed concentrations in fatal and nonfatal cases involving 37 novel synthetic opioids.

CONCLUSIONS

Blood levels of new opioids are extremely difficult to interpret. Low blood concentrations of these substances do not rule out acute poisoning as their high potency creates a risk of respiratory depression even at low doses. Opioid tolerance, frequent presence of other drugs, and additional diseases make it impossible to define concentration ranges, especially the minimum fatal concentrations. This report provides quick access to the source articles quantifying novel synthetic opioids.

Are the N-demethylated metabolites of U-47700 more active than their parent compound? In vitro μ-opioid receptor activation of N-desmethyl-U-47700 and N,N-bisdesmethyl-U-47700

Studies on the tissue distribution of the new synthetic opioid U-47700 and its main metabolite N-desmethyl-U-47700 revealed about sixfold higher metabolite concentrations in pig brain as compared with the parent compound. To better assess the toxic potential of this drug, the aim of this study was to assess the in vitro μ-opioid receptor (MOR) activation potential of the main metabolites of U-47700, N-desmethyl-U-47700, and N,N-bisdesmethyl-U-47700, using a live cell-based reporter assay based on NanoLuc Binary Technology®. Cells stably expressing human MOR and β-arrestin 2 (βarr2), each fused via a flexible linker to two complementary inactive subunits of the nanoluciferase, were seeded on poly-d-lysine-coated 96-well plates and treated with N-desmethyl-U-47700, N,N-bisdesmethyl-U-47700, U-47700, or hydromorphone as reference standard. MOR activation results in functional complementation of the nanoluciferase, which can be assessed via luminescence monitoring. The potency of the metabolites is lower than that of U-47700 (EC₅₀ of 186 nM for U-47700, 3770 nM for N-desmethyl-U-47700, and >5 μM for N,N-bisdesmethyl-U-47700). The maximal efficacy (E_max ) observed (relative to hydromorphone, set arbitrarily at 100%) decreased from 183% to 127% and 39.2% for U-47700, N-desmethyl-U-47700, and N,N-bisdesmethyl-U-47700, respectively. Thus, the loss of one or two methyl groups reduced the MOR activation potential, which was more pronounced if both methyl groups were removed. It is thus anticipated that the impact on MOR exerted by the higher metabolite concentration in brain has only little-if any relevance for the strong toxic effects of U-47700.

Perimortem Distribution of U-47700, Tramadol and their Main Metabolites in pigs Following Intravenous Administration

In spite of a decreasing number of new releases, New Synthetic Opioids (NSO) are gaining increasing importance in postmortem (PM) forensic toxicology. For the interpretation of analytical results, toxicokinetic (TK) data, e.g. on tissue distribution, are helpful. Concerning NSO, such data are usually not available due to the lack of controlled human studies. Hence, a controlled TK study using pigs was carried out and the tissue distribution of U-47700 and tramadol as reference was examined. Twelve pigs received an intravenous dose of 100 µg/kg body weight (BW) U-47700 or 1000 µg/kg BW tramadol, respectively. Eight hours after administration, the animals were put to death with T61. Relevant organs, body fluids and tissues were sampled. After homogenization and solid-phase extraction, quantification was performed applying standard addition and liquid chromatography-tandem mass spectrometry. At the time of death, the two parent compounds were determined in all analyzed specimens. Regarding U-47700, concentrations were highest in duodenum content, bile fluid and adipose tissue (AT). Concerning tramadol, next to bile fluid and duodenum content, highest concentrations were determined in the lung. Regarding the metabolites, N-desmethyl-U-47700 and O-desmethyltramadol (ODT) were detected in all analyzed specimens except for AT (ODT). Higher metabolite concentrations were found in specimens involved in metabolism. N-desmethyl-U-47700 showed much higher concentrations in routinely analyzed organs (lung, liver, kidney) than U-47700. To conclude, besides the routinely analyzed specimens in PM toxicology, AT, bile fluid and duodenum content could serve as alternative matrices for blood, urine or standard specimens such as kidney or liver. In case of U-47700, quantification of the main metabolite N-desmethyl-U-47700 is highly recommendable.

Analysis of the Illicit Opioid U-48800 and Related Compounds by LC-MS/MS and Case Series of Fatalities Involving U-48800

We report a method for the detection and quantitation of twelve drugs and two metabolites in the same structural class as the illicit mu-opioid agonist U-47700 in human whole blood. These substances are either known or suspected to be present as potential novel opioids in illicit drug markets. The general class of these drugs was developed in pharmaceutical research programs in the 1970's but have recently become of concern for overdoses and death in opioid users in the United States and internationally. The scope of analysis included the following compounds: methylenedioxy U-47700, ethylenedioxy U-47700, ethylenedioxy U-51754, U-69593, U-47931E (Bromadoline), U-47700, U-48800, U-49900, U-51754, U-50488, propyl U-47700, and isopropyl U-47700. Additionally, two metabolites, N,N-didesmethyl U-47700, desmethyl U-47700 were also included in the scope. Drugs were extracted from human whole blood using solid phase extraction (SPE) and the extracts were analyzed by liquid chromatography tandem mass spectrometry (LCMSMS). The assay was validated with respect to bias, carryover, interference, and within run and between run precision, and accuracy. Eight medicolegal death investigation cases which had screened positive for U-48800 by liquid chromatography time-of-flight mass spectrometry (LCTOF) were successfully confirmed and quantified using this method. The mean and median concentrations of U-48800 in these cases were 2.5 (±2.1) ng/mL and 1.8 ng/mL, respectively, with a range of concentrations of 0.27-6.2 ng/mL. Case history information including the presence of other drugs in combination are described and discussed.

Classics in Chemical Neuroscience: U-47700

U-47700, 3,4-dichloro-N-((1R,2R)-2-(dimethylamino)cyclohexyl)-N-methyl benzamide, is a novel synthetic opioid (NSO), discovered by the Upjohn company in the late 1970s. With potent in vivo activity, ∼10-times greater than that of morphine, U-47700 has become a drug of widespread abuse due to its ease of synthesis and, until recently, lack of robust detection methods by law enforcement. U-47700 has been found in counterfeit oxycodone tablets and is a key ingredient in "gray death." Due to its emergence worldwide in the past 5 years, it is now a Schedule I drug in the United States and similarly designated around the world; moreover, at autopsy, U-47700 was found to have contributed to the death of the pop artist Prince. This Review will capture the >40 year history of U-47700 and go in-depth regarding the synthesis, medicinal chemistry, in vitro/in vivo pharmacology, drug metabolism (from postmortem overdose cases), and societal impact of this DARK Classic in chemical neuroscience.

Designer drugs: mechanism of action and adverse effects

Psychoactive substances with chemical structures or pharmacological profiles that are similar to traditional drugs of abuse continue to emerge on the recreational drug market. Internet vendors may at least temporarily sell these so-called designer drugs without adhering to legal statutes or facing legal consequences. Overall, the mechanism of action and adverse effects of designer drugs are similar to traditional drugs of abuse. Stimulants, such as amphetamines and cathinones, primarily interact with monoamine transporters and mostly induce sympathomimetic adverse effects. Agonism at μ-opioid receptors and γ-aminobutyric acid-A (GABAA) or GABAB receptors mediates the pharmacological effects of sedatives, which may induce cardiorespiratory depression. Dissociative designer drugs primarily act as N-methyl-D-aspartate receptor antagonists and pose similar health risks as the medically approved dissociative anesthetic ketamine. The cannabinoid type 1 (CB1) receptor is thought to drive the psychoactive effects of synthetic cannabinoids, which are associated with a less desirable effect profile and more severe adverse effects compared with cannabis. Serotonergic 5-hydroxytryptamine-2A (5-HT2A) receptors mediate alterations of perception and cognition that are induced by serotonergic psychedelics. Because of their novelty, designer drugs may remain undetected by routine drug screening, thus hampering evaluations of adverse effects. Intoxication reports suggest that several designer drugs are used concurrently, posing a high risk for severe adverse effects and even death.

Novel synthetic opioids - toxicological aspects and analysis

Over the past few years, there has been an emerging number of new psychoactive drugs. These drugs are frequently mentioned as "legal highs", "herbal highs", "bath salts" and "research chemicals". They are mostly sold and advertised on online forums and on the dark web. The emerging new psychoactive substances are designed to mimic the effects of psychoactive groups, which are often abused drugs. Novel synthetic opioids are a new trend in this context and represent an alarming threat to public health. Given the wide number of fatalities related to these compounds reported within the last few years, it is an important task to accurately identify these compounds in biologic matrices in order to administer an effective treatment and reverse the respiratory depression caused by opioid related substances. Clinicians dealing with fentanyl intoxication cases should consider that it could, in fact, be a fentanyl analogue. For this reason, it is a helpful recommendation to include synthetic opioids in the routine toxicological screening procedures, including analysis in alternative matrices, if available, to investigate poly-drug use and possible tolerance to opioids. To address this public health problem, better international collaboration, effective legislation, effective investigation, control of suspicious "research chemicals" online forums and continuous community alertness are required. This article aims to review diverse reported fatalities associated with new synthetic opioids describing them in terms of pharmacology, metabolism, posology, available forms, as well as their toxic effects, highlighting the sample procedures and analytical techniques available for their detection and quantification in biological matrices.

Non-Medical Use of Novel Synthetic Opioids: A New Challenge to Public Health

Background: In the last decade there has been a progressive increase in the use of new psychoactive substances (NPSs) that are not yet under international control. In particular, novel synthetic opioids (NSOs) have reappeared on the recreational drug market in the last few years. As a result, the use of NSOs has increased rapidly. This poses an emerging and demanding challenge to public health. Aim: To raise awareness among clinicians and other professionals about NPSs, especially NSOs, to summarize current knowledge about pharmacological properties, forms of NSO on the market, pattern of use, effects and consequences of use. Methods: An electronic search was carried out on the Medline/PubMed and Google Scholar databases to find selected search terms. Results: Some NPSs are already controlled, while others can be legally sold directly on the drug market (mainly via internet, less so by drug dealers) or be used as precursors for the synthesis of other designer drugs that mimic the psychoactive effects of controlled substances. Potential side-effects of NSOs include miosis, sedation, respiratory depression, hypothermia, inhibition of gastrointestinal propulsion, death (from opioid overdose). Conclusions: The severity of the opioid crisis has intensified with the introduction of highly potent NSOs on the drug market. As long as addicts are dying from overdose or similar causes, there is something more constructive to do than waiting for addicts to overdose on heroin at a place located near a remedy, as if to say, within reach of naloxone.

The search for the "next" euphoric non-fentanil novel synthetic opioids on the illicit drugs market: current status and horizon scanning

PURPOSE

A detailed review on the chemistry and pharmacology of non-fentanil novel synthetic opioid receptor agonists, particularly N-substituted benzamides and acetamides (known colloquially as U-drugs) and 4-aminocyclohexanols, developed at the Upjohn Company in the 1970s and 1980s is presented.

METHOD

Peer-reviewed literature, patents, professional literature, data from international early warning systems and drug user fora discussion threads have been used to track their emergence as substances of abuse.

RESULTS

In terms of impact on drug markets, prevalence and harm, the most significant compound of this class to date has been U-47700 (trans-3,4-dichloro-N-[2-(dimethylamino)cyclohexyl]-N-methylbenzamide), reported by users to give short-lasting euphoric effects and a desire to re-dose. Since U-47700 was internationally controlled in 2017, a range of related compounds with similar chemical structures, adapted from the original patented compounds, have appeared on the illicit drugs market. Interest in a structurally unrelated opioid developed by the Upjohn Company and now known as BDPC/bromadol appears to be increasing and should be closely monitored.

CONCLUSIONS

International early warning systems are an essential part of tracking emerging psychoactive substances and allow responsive action to be taken to facilitate the gathering of relevant data for detailed risk assessments. Pre-emptive research on the most likely compounds to emerge next, so providing drug metabolism and pharmacokinetic data to ensure that new substances are detected early in toxicological samples is recommended. As these compounds are chiral compounds and stereochemistry has a large effect on their potency, it is recommended that detection methods consider the determination of configuration.

Case report: relevance of metabolite identification to detect new synthetic opioid intoxications illustrated by U-47700

Today, new psychoactive substances (NPS) producers increasingly appear to be targeting new synthetic opioids (NSOs), and the recent emergence of NSOs is causing considerable concern in North America and in Europe. For toxicologists, NSO detection in a forensic context presents three additional difficulties to the general NPS analytical detection challenge: (i) high frequency of new products, (ii) low concentrations (in μg/L range and under) in biological samples related to their high opioid potency, and (iii) extensive metabolism. In this context, the present work aims to highlight the relevance of NSO metabolite detection in potential intoxication cases. Illustration is given with U-47700, an emerging NSO, (i) that was identified in a powder recently collected in France and in a fatality case, (ii) whose metabolites were in vitro produced using human liver microsomes and their mass spectra (MS) added in our MS/MS and HRMS libraries, and (iii) for which metabolism data were compared to those of the literature: U-47700 was identified in the powder and at 3040 μg/L in peripheral blood in the fatality case. In addition, high amounts of several U-47700 metabolites, especially N-desmethyl-U-47700, were observed in urine. Even if metabolite formation may largely depend on the enzymatic activity as well as on the length of the survival time, confrontation of these results to data found in the literature strongly suggests that this metabolite is regularly a better blood and (mainly) urine biomarker of U-47700 intake than U-47700 itself. Indeed, in this fatality and in other previous reports, N-desmethyl-U-47700 produced the main observed chromatographic signal (i) systematically in vitro and (ii) commonly in vivo, especially in urines. N,N-Didesmethyl-U-47700 is also sometimes a better biomarker of U-47700 intake than U-47700 itself. Accordingly, we suggest adding N-desmethyl-U-47700 (and N,N-didesmethyl-U-47700) in mass spectrum databases used for toxicological screening in order to reduce the risk of false-negative results in intoxication cases involving U-47700.

Newly Emerging Drugs of Abuse and Their Detection Methods: An ACLPS Critical Review

Objectives

Illicit drug abuse has reached an epidemic level in the United States. Drug overdose has become the leading cause of injury-related deaths since 2008 due to the recent surge of opioid overdose by heroin, controlled prescription drugs, and nonmethadone synthetic opioids. Synthetic designer drugs such as synthetic cathinones ("bath salts") and synthetic cannabinoids ("Spice" and "K2") continue to emerge and attract recreational users.

Methods

The emergence of new drugs of abuse poses a steep challenge for clinical toxicology laboratories. Limited information about the emerging drugs and their metabolism, "rebranding" of the illicit drugs, and a lack of Food and Drug Administration-approved screening methods for these drugs contribute to this difficulty. Here we review detection methods that can aid in identifying emerging drugs of abuse.

Results

One promising approach is the utilization of untargeted drug screening by mass spectrometry. Historically, gas chromatography-mass spectrometry has been the gold standard.

Conclusions

Liquid chromatography-tandem mass spectrometry and liquid chromatography-high-resolution mass spectrometry offer improved detection capability of new drugs with simplified sample preparation, making it the new standard.

Near-fatal Intoxication with the "New" Synthetic Opioid U-47700: The First Reported Case in the Czech Republic

Recreational use of the potent synthetic opioid 3,4- dichloro-N-(2-(dimethylamino)cyclohexyl)-N-methylbenzamide (U-47700) is rising, accompanied by increasingly frequent cases of serious intoxication. This article reports a case of near-fatal U-47700 intoxication. A man was found unconscious (with drug powder residues). After 40 h in hospital (including 12 h of supported ventilation), he recovered and was discharged. Liquid chromatography/high-resolution mass spectrometry (LC/HRMS) or gas chromatography/mass spectrometry (GC/MS) were used to detect and quantify substances in powders, serum and urine. Powders contained U-47700 and two synthetic cannabinoids. Serum and urine were positive for U-47700 (351.0 ng/mL), citalopram (<LOQ), tetrahydrocannabinol (THC: 3.3 ng/mL), midazolam (<LOQ) and a novel benzodiazepine, clonazolam (6.8 ng/mL) and their metabolites but negative for synthetic cannabinoids. If potent synthetic opioids become cheaper and more easily obtainable than their classical counterparts (e.g., heroin), they will inevitably replace them and users may be exposed to elevated risks of addiction and overdose.

Novel Synthetic Opioids: The Pathologist's Point of View

Background: New Psychoactive Substances (NPS) constitute a broad range of hundreds of natural and synthetic drugs, including synthetic opioids, synthetic cannabinoids, synthetic cathinones, and other NPS classes, which were not controlled from 1961 to 1971 by the United Nations drug control conventions. Among these, synthetic opioids represent a major threat to public health. Methods: A literature search was carried out using public databases (such as PubMed, Google Scholar, and Scopus) to survey fentanyl-, fentanyl analogs-, and other synthetic opioid-related deaths. Keywords including “fentanyl”, “fentanyl analogs”, “death”, “overdose”, “intoxication”, “synthetic opioids”, “Novel Psychoactive Substances”, “MT-45”, “AH-7921”, and “U-47700” were used for the inquiry. Results: From our literature examination, we inferred the frequent implication of fentanyls and synthetic opioids in side effects, which primarily affected the central nervous system and the cardiovascular and pulmonary systems. The data showed a great variety of substances and lethal concentrations. Multidrug-related deaths appeared very common, in most reported cases. Conclusions: The investigation of the contribution of novel synthetic opioid intoxication to death should be based on a multidisciplinary approach aimed at framing each case and directing the investigation towards targeted toxicological analyses.

Activity-Based Concept to Screen Biological Matrices for Opiates and (Synthetic) Opioids

BACKGROUND

Detection of new highly potent synthetic opioids is challenging as new compounds enter the market. Here we present a novel screening method for the detection of opiates and (synthetic) opioids based on their activity.

METHODS

A cell-based system was set up in which activation of the μ-opioid receptor (MOR) led to recruitment of β-arrestin 2, resulting in functional complementation of a split NanoLuc luciferase and allowing readout via bioluminescence. Assay performance was evaluated on 107 postmortem blood samples. Blood (500 μL) was extracted via solid-phase extraction. Following evaporation and reconstitution in 100 μL of Opti-MEM® I, 20 μL was analyzed in the bioassay.

RESULTS

In 8 samples containing synthetic opioids, in which no positive signal was obtained in the bioassay, quadrupole time-of-flight mass spectrometry revealed the MOR antagonist naloxone, which can prevent receptor activation. Hence, further evaluation did not include these samples. For U-47700 (74.5–547 ng/mL) and furanyl fentanyl (&lt;1–38.8 ng/mL), detection was 100% (8/8) for U-47700 and 95% (21/22) for furanyl fentanyl. An analytical specificity of 93% (55/59) was obtained for the opioid negatives. From an additional 10 samples found to contain other opioids, 5 were correctly scored positive. Nondetection in 5 cases could be explained by very low concentrations (&lt;1 ng/mL alfentanil/sufentanil) or presence of inactive enantiomers.

CONCLUSIONS

The MOR reporter assay allows rapid identification of opioid activity in blood. Although the cooccurrence of opioid antagonists is currently a limitation, the bioassay's high detection capability, specificity, and untargeted nature may render it a useful first-line screening tool to investigate potential opioid intoxications.

Synthetic Opioids

Opioid abuse has been a global menace for centuries, but the proliferation of synthetic opioids and their use within this current decade have created epidemic-level harms in some countries. According to the United Nations Office on Drugs and Crime, almost 12 million years were estimated loss of "healthy" life resulting in premature death and disability attributable to global opioid abuse just in 2015. Law enforcement and regulatory authorities have been particularly challenged abating the spread of synthetic opioids because soon after controlling the currently recognized abused opioids, their structures are tweaked, and new entities replace them. Drug racketeers have most often exploited the fentanyl phenylpiperidine structure in this regard, but non-fentanyl-like and classical morphinan-like structures have been pirated as well. A growing number of anecdotal reports identify respiratory depression induced by these newer synthetic opioids to be especially refractive to reversal by antagonists, with consequently high levels of lethality. This review examines three of these synthetic opioids representing three chemical classes (U-47700, MT-45, and acetylfentanyl) that have emerged to be of such menace that they have been brought under international control in recent years and addresses factors that could make synthetic opioids especially untreatable by opioid antagonists.

A Novel Oral Fluid Assay (LC-QTOF-MS) for the Detection of Fentanyl and Clandestine Opioids in Oral Fluid After Reported Heroin Overdose

INTRODUCTION

The adulteration of heroin with non-pharmaceutical fentanyl and other high-potency opioids is one of the factors contributing to striking increases in overdose deaths. To fully understand the magnitude of this problem, accurate detection methods for fentanyl and other novel opioid adulterant exposures are urgently required. The objective of this work was to compare the detection of fentanyl in oral fluid and urine specimens using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) in a population of heroin users presenting to the Emergency Department after overdose.

METHODS

This was a prospective observational study of adult Emergency Department patients who presented after a reported heroin overdose requiring naloxone administration. Participants provided paired oral fluid and urine specimens, which were prepared, extracted, and analyzed using a dual LC-QTOF-MS workflow for the identification of traditional and emerging drugs of abuse. Analytical instrumentation included SCIEX TripleTOF® 5600+ and Waters Xevo® G2-S QTOF systems.

RESULTS

Thirty participants (N = 30) were enrolled during the study period. Twenty-nine participants had fentanyl detected in their urine, while 27 had fentanyl identified in their oral fluid (overall agreement 93.3%, positive percent agreement 93.1%). Cohen's Kappa (k) was calculated and demonstrated moderately, significant agreement (k = 0.47; p value 0.002) in fentanyl detection between oral fluid and urine using this LC-QTOF-MS methodology. Additional novel opioids and metabolites, including norfentanyl, acetylfentanyl, and U-47700, were detected during this study.

CONCLUSION

In this study of individuals presenting to the ED after reported heroin overdose, a strikingly high proportion had a detectable fentanyl exposure. Using LC-QTOF-MS, the agreement between paired oral fluid and urine testing for fentanyl detection indicates a role for oral fluid testing in surveillance for nonpharmaceutical fentanyl. Additionally, the use of LC-QTOF-MS allowed for the detection of other clandestine opioids (acetylfentanyl and U-47700) in oral fluid.

Fentanyl, fentanyl analogs and novel synthetic opioids: A comprehensive review

Deaths from opioid use are increasing in the US, with a growing proportion due to synthetic opioids. Until 2013, sporadic outbreaks of fentanyl and fentanyl analogs contaminating the heroin supply caused some deaths in heroin users. Since then, fentanyl has caused deaths in every state and fentanyl and its analogs have completely infiltrated the North American heroin supply. In 2014, the first illicit pills containing fentanyl, fentanyl analogs, and other novel synthetic opioids such as U-47700 were detected. These pills, which look like known opioids or benzodiazepines, have introduced synthetic opioids to more unsuspecting customers. As soon as these drugs are regulated by various countries, new compounds quickly appear on the market, making detection difficult and the number of cases likely underreported. Standard targeted analytical techniques such as GC-MS (gas chromatography mass spectrometry) and LC-MS/MS (liquid chromatography tandem mass spectrometry) can detect these drugs, but novel compound identification is aided by nontargeted testing with LC-HRMS (liquid chromatography high resolution mass spectrometry). Fentanyl, fentanyl analogs and other novel synthetic opioids are all full agonists of varying potencies at the μ-opioid receptor, leading to typical clinical effects of miosis and respiratory and central nervous system depression. Due to their high affinity for μ-opioid receptors, larger doses of naloxone are required to reverse the effects than are commonly used. Synthetic opioids are an increasingly major public health threat requiring vigilance from multiple fields including law enforcement, government agencies, clinical chemists, pharmacists, and physicians, to name a few, in order to stem its tide. This article is part of the Special Issue entitled 'Designer Drugs and Legal Highs.'

Metabolism of novel opioid agonists U-47700 and U-49900 using human liver microsomes with confirmation in authentic urine specimens from drug users

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 U-47700, and five metabolites for U-49900. N-Desmethyl-U-47700 was determined to be the primary metabolite of U-47700. Parent U-47700 was identified in all urine specimens. N-Desmethyl-U-47700 and N,N-didesmethyl-U-47700 were structurally confirmed for the first time during this study following acquisition of standard reference material. N-Desethyl-U-49900 was determined to be the primary metabolite of U-49900 following microsomal incubations, while N,N-didesethyl-N-desmethyl-U-49900 was the most abundant in a urine specimen. Similarities in metabolic transformation were identified between U-47700 and U-49900, resulting in a common metabolite and isomeric species. These phenomena should be considered in cases involving U-47700 or U-49900. This study is the first to map the metabolic profiles of U-47700 and U-49900 using human liver microsomes, as well as the first to report any literature involving U-49900 and analysis of case specimens.

Misuse of Novel Synthetic Opioids: A Deadly New Trend

Novel synthetic opioids (NSOs) include various analogs of fentanyl and newly emerging non-fentanyl compounds. Together with illicitly manufactured fentanyl (IMF), these drugs have caused a recent spike in overdose deaths, whereas deaths from prescription opioids have stabilized. NSOs are used as stand-alone products, as adulterants in heroin, or as constituents of counterfeit prescription medications. During 2015 alone, there were 9580 deaths from synthetic opioids other than methadone. Most of these fatalities were associated with IMF rather than diverted pharmaceutical fentanyl. In opioid overdose cases, where the presence of fentanyl analogs was examined, analogs were implicated in 17% of fatalities. Recent data from law enforcement sources show increasing confiscation of acetylfentanyl, butyrylfentanyl, and furanylfentanyl, in addition to non-fentanyl compounds such as U-47700. Since 2013, deaths from NSOs in the United States were 52 for acetylfentanyl, 40 for butyrylfentanyl, 128 for furanylfentanyl, and 46 for U-47700. All of these substances induce a classic opioid toxidrome, which can be reversed with the competitive antagonist naloxone. However, due to the putative high potency of NSOs and their growing prevalence, it is recommended to forgo the 0.4 mg initial dose of naloxone and start with 2 mg. Because NSOs offer enormous profit potential, and there is strong demand for their use, these drugs are being trafficked by organized crime. NSOs present major challenges for medical professionals, law enforcement agencies, and policymakers. Resources must be distributed equitably to enhance harm reduction though public education, medication-assisted therapies, and improved access to naloxone.