New synthetic opioids: Part of a new addiction landscape.

Synthetic opioids (SO) are a major risk for public health across the world. These drugs can be divided into 2 categories, pharmaceutical and non-pharmaceutical fentanyls. A new generation of SO has emerged on the drug market since 2010. North America is currently facing an opioid epidemic of morbi-mortality, caused by over-prescription of opioids, illegally diverted prescribed medicines, the increasing use of heroin and the emergence of SO. Furthermore, this opioid crisis is also seen in Europe. SO are new psychoactive substances characterized by different feature such as easy availability on the Internet, low price, purity, legality, and lack of detection in laboratory tests. They have not been approved or are not recommended for human use. Opioid misuse is associated with somatic and psychiatric complications. For many substances, limited pharmacological information is available, increasing the risk of harmful adverse events. Health actors and the general population need to be clearly informed of the potential risks and consequences of the diffusion and use of SO.

Brain disposition, metabolism and behavioral effects of the synthetic opioid AH-7921 in rats.

3,4-Dichloro-N-benzamide (AH-7921) is a cyclohexyl-methylbenzamide derivative with analgesic activity, whose abuse was associated with several fatal intoxications, included in Schedule I of UN Single Convention on Narcotic Drugs. We validated an HPLC-MS/MS method to investigate its brain disposition and metabolism after single and repeated injections; in parallel, we evaluated its central behavioral effects. After an intraperitoneal injection of 10 mg/kg, the analgesic effect appeared after 5 min and persisted up to 4 h; brain absorption was rapid (tmax 30 min) and large (brain-to-plasma ratio 16), with active concentration >700 ng/g. By high-resolution MS we identified several metabolites in plasma and brain, the most important being N-demethylated and N,N-didemethylated metabolites; they showed high brain permeability, although they probably do not contribute to the analgesic effect of the parent compound (brain tmax>2 h). Starting 2 h after treatment, the two metabolites showed higher plasma and brain concentrations than the parent molecule, which persisted much longer, and could be used to evaluate drug intake in human consumers. Tolerance was observed after seven daily doses, when the compound's analgesic effect was 14% lower than after the first dose; since brain concentrations did not decrease in parallel, the development of pharmacodynamic tolerance can be suggested. However, pharmacokinetic tolerance is also likely, as brought to light by the data after a dose challenge, given after a 48 h washout period from the 7th dose, showing a lower brain-to-plasma ratio. We also describe the rewarding effect of AH-7921 (conditioned place preference), suggesting a high risk of addiction in humans.

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.

AH-7921: A review of previously published reports.

AH-7921 is a synthetic opioid that was developed in the early 1970s. It has resulted in several fatal and nonfatal intoxications, despite not having approval from the US Food and Drug Administration. To date, AH-7921 is listed as a schedule I drug, and there have been no clinical trials exploring the safety of AH-7921. Herein, we provide an analysis of existing case reports available in the literature regarding AH-7921. We searched PubMed, Scopus, Web of Science, and EBSCO for articles (up until December 2017) using the terms "AH-7921" and "AH7921." In total, 48 articles were identified, and 5 articles were included in our review. A total of 14 cases were found, of which 13 resulted in fatalities. The oral route of administration was reported in two cases, and most cases reported use of concomitant pharmaceutical agents. Pulmonary edema was the most common finding postmortem among deceased cases, with nine of the cases having heavier lungs. Overall, fatalities occurred with low and high concentrations of AH-7921 in the femoral blood. We strongly encourage toxicology screenings for this novel opioid to be included when an overdose of an opioid of unknown nature is suggested.

Rewarding and reinforcing effects of 4-chloro-2,5-dimethoxyamphetamine and AH-7921 in rodents.

New psychoactive substances (NPSs), i.e., newly designed substances with chemical residues that are slightly different from those of known psychoactive substances, have been emerging since the late 2000s, and social problems related to the use of these substances are increasing globally. Two such NPSs are 4-chloro-2,5-dimethoxyamphetamine (DOC), a psychedelic substance that is structurally related to amphetamine, and AH-7921, an opioid analgesic that is used for recreational purposes and has a potency similar to that of morphine. Currently, scientific evidence for the dependence liability or toxicity of NPSs is lacking. Therefore, in this study, we performed animal behavioral tests to evaluate the dependence liability of DOC and AH-7921. The rewarding and reinforcing effects of DOC and AH-7921 were evaluated using the conditioned place preference (CPP) paradigm in mice and the self-administration (SA) procedure in rats. Both DOC and AH-7921 increased the preference for the drug-paired compartment in the CPP test at a dose of 0.3 mg/kg and increased the number of responses to the active lever in the SA test at 0.01 mg/(kg·infusion). Collectively, the data suggest that DOC and AH-7921 may have both rewarding and reinforcing effects. Further studies are needed to confirm the reinforcing effects in broader dose ranges with various schedules.

Pharmacotoxicology of Non-fentanyl Derived New Synthetic Opioids.

A class of opioid agonists not structurally related to fentanyl, derived from research publications of pharmaceutical companies or patents within the United States and abroad are contributing to the current opioid epidemic. Novel synthetic opioids (NSOs) created to circumvent drug control laws such as U-47700, U-49900, AH-7921, or MT-45 have no recognized therapeutic use, are clandestinely manufactured and sold on conventional or dark web. We herein provide a review of the pharmacological properties available on most of these substances trying to provide a better knowledge on these compounds, particularly with respect to toxicity and dangerous adverse effects in users. Indeed, these NSOs share not only a great potency of action and receptor affinity with respect to natural or synthetic opiates (e.g., morphine, heroin, and methadone) but also a non-negligible toxicity leading to intoxications and fatalities, posing a serious harm to public health and society.

Opioids in the Frame of New Psychoactive Substances Network: A Complex Pharmacological and Toxicological Issue.

BACKGROUND: New psychoactive substances (NPS), often referred to as "legal highs" or "designer drugs", are derivatives and analogues of existing psychoactive drugs that are introduced in the recreational market to circumvent existing legislation on drugs of abuse. OBJECTIVE: This systematic review aims to gather the state of the art regarding chemical, molecular pharmacology and toxicological information of opioid class of NPS. METHODS: Chemical, pharmacological, toxicological and clinical effects of opioid class of NPS were searched in books and in PubMed (U.S. National Library of Medicine) without a limiting period. RESULTS: Within this class, fentanyl analogues are among the most frequently abused and pose several clinical concerns and therefore will be thoroughly discussed. Other opioid sub-categories of NPS frequently misused include AH-7921, MT-45, U-47700, U-50488, desomorphine, mitragynine, tramadol, tapentadol, salvinorin A and its analogue herkinorin. CONCLUSION: Due to inefficient monitoring techniques, as well as limited knowledge regarding the acute and long-term effects of opioids NPS, further clinical and forensic toxicological studies are required.

Reaching out for Sensitive Evaluation of the Mu Opioid Receptor in Vivo: Positron Emission Tomography Imaging of the Agonist [11C]AH7921.

Imaging of the mu opioid receptor (MOR) availability with positron emission tomography (PET) is a pertinent challenge in Neuroscience. Both, regulation of receptor expression and occupancy by endogeneous opioids play into cognitive and behavioral phenotypes of healthy function and disease. Receptor expression in the active and inactive states can be measured using high affinity radioagonist and radioantagonist PET tracers, respectively. Occupancy assessment requires radioligands showing competitive and reversible binding with moderate affinity to the MOR, which may lead to physical extinction of the receptor specific signal in vivo. We investigated a moderately potent, selective MOR agonist in rat to test if a radiotracer design paradigm tailored to competition with endogeneous opioids leads to viable imaging results. The benzamide 3,4-dichlorobenzenecarboxylic acid (dimethylamino)cyclohexyl)methyl amide (AH-7921, 1) was synthesized and characterized in rat brain using autoradiography and positron emission tomography. Compound 1 was found to activate with low nanomolar potency the MOR and to a lesser extent KOR as a full agonist. Concentration dependent binding studies with agonist and antagonist radioligands were conducted to assess competition behavior and obtain inhibition constants. Kinetic analysis of 3,4-dichlorobenzene[11C]carboxylic acid (dimethylamino)cyclohexyl)methyl amide binding in rat brain resulted in low but reproducible binding potential in the thalamus (0.8 ± 0.1). A radioactive metabolite was detected in brain (17%, after 15 min). Nonetheless, we conclude that quantitative imaging of MOR availability is possible when using a moderate affinity radiotracer.

An Expanding World of Novel Psychoactive Substances: Opioids.

The abuse of novel psychoactive substances (NPS) has been increasing dramatically worldwide since late 2000s. By the end of 2015, more than 560 NPS had been reported to the European Monitoring Centre for Drugs and Drug Addiction. Although the most popular compounds are synthetic cannabinoids and psychostimulatory derivatives of cathinone (so-called ß-keto-amphetamines), novel synthetic opioids have recently emerged on the recreational drug market. They include fentanyl (a potent narcotic analgesic) and its analogs (e.g., acetylfentanyl, acryloylfentanyl, carfentanil, α-methylfentanyl, 3-methylfentanyl, furanylfentanyl, 4-fluorobutyrylfentanyl, 4-methoxybutyrylfentanyl, 4-chloroisobutyrylfentanyl, 4-fluoroisobutyrylfentanyl, tetrahydrofuranylfentanyl, cyclopentylfentanyl, and ocfentanil) and compounds with different chemical structures, such as AH-7921, MT-45, and U-47700. This survey provides an overview of the pharmacological properties, pattern of use, and desired and unwanted effects of the above-listed novel opioids. Special emphasis is given to cases of non-fatal and lethal intoxication involving these compounds.

Two fatalities associated with synthetic opioids: AH-7921 and MT-45.

In this study, two fatalities associated with the synthetic opioids AH-7921 and MT-45 are reported. Within the last few years, both compounds have emerged on the recreational drug market and are sold as "research chemicals" on the internet. In the first case, a 22-year-old woman was found dead in the bedroom of her apartment by two of her friends. A plastic bag labeled "AH-7921" was found in the apartment and the two friends stated that the deceased had consumed AH-7921 prior to her death. The woman was a known drug addict. In the second case, a 24-year-old man was found dead in his room by his mother. The deceased was sitting on a chair in front of his desk slumped over. Several bags of white powder labeled "MT-45", "Methoxmetamine" and "Methoxphenidine" were found in his room. Toxicological analyses of femoral blood, heart blood, liver, pericardial fluid, urine, vitreous humor and stomach content of the deceased were performed using liquid chromatography-quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS). Time-of-flight mass spectrometry was carried out on an LC-Triple TOF 5600 system (AB Sciex) with electrospray ionization operated in positive mode. In the first case, additional hair analysis was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and LC-QTOF-MS. In both cases, the relevant synthetic opioid could be detected in all analyzed samples. The concentration of AH-7921 was determined to be 450µg/L in femoral blood. MT-45 was present at a concentration of 2900µg/L in femoral blood. Besides methoxmetamine which could qualitatively be detected in femoral blood, urine and stomach content no methoxphenidine was found. In summary, deaths of the young individuals could be, by exclusion of other causes of death, attributed to the consumption of an overdose of AH-7921 and MT-45, respectively.

AH-7921: the list of new psychoactive opioids is expanded.

AH-7921 is a structurally unique synthetic opioid analgesic that has recently entered the drug arena in Europe, the USA, and Japan. Although it was synthesized and patented in the mid-1970s, it was first identified in a seized sample purchased via the Internet in July 2012 and formally brought to the attention of the European Union early warning system in August 2012 by the United Kingdom. Several in vitro experiments and animal model studies established the morphine-like analgesic action of AH-7921 as a µ-opioid receptor agonist that has been found to be several times more potent than codeine and at least as potent as morphine. This novel psychoactive substance has already led to eight non-fatal intoxications and 16 deaths in Sweden, the United Kingdom, Norway, and the USA. Thus, AH-7921 is a current public health risk, and better international collaboration, effective legislation and continuous community alertness are needed to tackle this current growing problem. The aim of this review is to summarize the current knowledge about this drug concerning its chemistry, pharmacology, and toxicology, as well as its international legal status. The limited existing analytical methodologies for the determination of AH-7921 in biological samples are also presented. Published or reported AH-7921-related cases, fatalities, or intoxications, and self reports from drug users are reviewed.

Lethal poisonings with AH-7921 in combination with other substances.

AH-7921 is a synthetic µ-opioid agonist, approximately equipotent with morphine. We report the death of two young individuals after ingestion of AH-7921 in combination with other psychoactive drugs. In the first case a young man died shortly after ingesting Internet drugs. Toxicological analysis of post mortem peripheral blood revealed AH-7921 (0.43 mg/L), 2-FMA (0.0069 mg/L) and 3-MMC (0.0021 mg/L) as well as codeine (0.42 mg/L), codeine-6-glucuronide (0.77 mg/L) and acetaminophen (18.7 mg/L). The second case involved a young female found dead at home. The only positive finding at medicolegal autopsy was needle marks. Toxicological analysis revealed AH-7921 (0.33 mg/L), methoxetamine (MXE) (0.064 mg/L), etizolam (0.27 mg/L), phenazepam (1.33 mg/L), 7-aminonitrazepam (0.043 mg/L), diazepam (0.046 mg/L), nordiazepam (0.073 mg/L), and oxazepam (0.018 mg/L) in blood. In both cases intoxication with AH-7921 in combination with other psychoactive drugs was considered to be the cause of death.