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Abstract Purpose Photoperiod determines the metabolic activity of brown adipose tissue (BAT) and affects the food intake and body mass of mammals. Sympathetic innervation of the BAT controls thermogenesis and facilitates physiological adaption to seasonal changes, but the exact mechanism remains elusive. Previous studies have shown that central opioid signaling regulates BAT thermogenesis, and that the expression of the brain mu-opioid receptor (MOR) varies seasonally. Therefore, it is important to know whether MOR expression in BAT shows seasonal variation. Methods We determined the effect of photoperiod on BAT MOR availability using [11C]carfentanil positron emission tomography (PET). Adult rats (n = 9) were repeatedly imaged under various photoperiods in order to simulate seasonal changes. Results Long photoperiod was associated with low MOR expression in BAT (β = − 0.04, 95% confidence interval: − 0.07, − 0.01), but not in muscles. We confirmed the expression of MOR in BAT and muscle using immunofluorescence staining. Conclusion Photoperiod affects MOR availability in BAT. Sympathetic innervation of BAT may influence thermogenesis via the peripheral MOR system. The present study supports the utility of [11C]carfentanil PET to study the peripheral MOR system.

The analysis of drugs in wastewater for forensic purposes has been constantly increasing and the investigation of the potential interaction between drugs or metabolites and sewage microbiota is important. The results demonstrated that cocaine esterase genes were widely distributed in 1142 global wastewater samples collected from 64 countries and linked to several bacterial species. In addition, in silico predictions indicated that carfentanil, 4F-MDMB-BINACA, 5F-MDMB-PICA, MDMB-4en-PINACA and mitragynine might also undergo microbial hydrolysis, in a similar fashion of cocaine degradation by cocaine esterase. In conclusion, it was demonstrated the microbial potential to hydrolyze drugs of abuse in wastewater environments, contributing to the critical evaluation of potential metabolites as biomarkers for microbial and human transformation of drugs in wastewater.

The proliferation of novel psychoactive substances (NPS) and the current opioid epidemic creates challenges for a toxicology laboratory. Methods capable of detecting and quantitating emerging compounds must be established despite limited information on toxicologically relevant concentrations. This paper will (i) describe how a publicly funded forensic laboratory reacted to the emergence of carfentanil as a public safety concern and (ii) contribute to the existing forensic literature by presenting a series of deaths involving carfentanil between July 2017 and June 2018. The Centre of Forensic Sciences is the primary provider of forensic toxicology testing in medicolegal death investigations in the province of Ontario. When carfentanil was first identified in the illicit drug supply, routine screening methods used by this laboratory were not sufficiently sensitive to detect the drug at concentrations expected in blood samples. Previously validated, multi-target liquid chromatography–tandem mass spectrometry (LC–MS-MS) quantitative methods already in use by the laboratory did show improved detectability for carfentanil. Thus, an existing LC–MS-MS method was adapted to include carfentanil, achieving improved sensitivity while also providing quantitation in suspected drug-related deaths. This approach had the added benefit that the LC–MS-MS method selected for modification was used in all death investigations requiring toxicology analysis in Ontario, thereby providing an opportunity for surveillance. Using this method, 4,953 cases were analyzed with carfentanil detected at a concentration greater than the limit of detection (0.05 ng/mL) in 160 decedents. Postmortem blood carfentanil concentrations ranged from less than 0.1 to 9.2 ng/mL. Of the 160 carfentanil-positive cases, 156 were classified as either mixed drug toxicity or carfentanil overdose. The approach described enabled this laboratory to efficiently implement a quantitative test for carfentanil in all death investigations, providing a useful template for modifying existing methods when a new psychoactive substance becomes available in the population.

The geometrical molecular structures, atomic charges, frontier molecular orbitals, and UV–visible electronic data of analgesic drugs carfentanil and acetylfentanyl were computed using quantum chemical code. In addition, NMR (1H and 13C) chemical shifts, harmonic vibrational wavenumbers, and the corresponding vibrational assignments were proposed on the basis of potential energy distribution. The calculations were carried out at Becke-3-Lee–Yang–Parr (B3LYP) functional with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using the 6–311 + + G(d,p) basis set. The piperidine rings of the two molecules adopt a more stable chair conformation of a six-membered ring structure with slight distortion at the point of substitution. This shows that the piperidine moiety of the carfentanil and acetylfentanyl have similar geometric parameters and thus support the hypothesis that the piperidine ring in these molecules is the primary structural feature that is responsible for their analgesic activities. In addition, the introduction of the carbomethoxy (-COCH3) group into the piperidine ring of fentanyl has little or no effect on the electronic properties of this class of molecules. The theoretical results were successfully compared with similar piperidine-based analgesic drugs fentanyl and available experimental data. This research gives precise and invaluable information that will help in the structural elucidation of analogs of fentanyl that could be used in the development of analytical methods for the accurate and reliable detection and monitoring of these important molecules.

Carfentanil is an ultra-potent opioid with an analgesic potency 10,000 times that of morphine but has received little scientific investigation. In the present study, the human cytochrome P450 (CYP) isozymes catalyzing the oxidative metabolism of carfentanil were investigated. Using UHPLC-HRMS, Michaelis-Menten kinetics of formation for three major metabolites norcarfentanil (M1), pharmaceutical active metabolite 4-[(1-oxopropyl)phenylamino]-1-(2-hydroxyl-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M11), and 4-[(1-oxopropyl)phenylamino]-1-(2-oxo-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M15) were determined. Isozymes catalyzing the formation of the low abundant, highly active metabolite 1-[2-(2-hydroxylphenyl)ethyl]-4-[(1-oxopropyl)phenylamino]-4-piperidinecarboxylic acid methyl ester (M13) were also identified. Selective P450 inhibition studies with pooled human liver microsomes (HLMs) and recombinant CYP isozymes suggested that metabolites M1, M11, and M15 were predominantly formed by isozyme CYP3A5, followed by CYP3A4. Isozymes CYP2C8 and CYP2C9 also made contributions but to a much lesser extent. Highly potent metabolite M13 was predominantly formed by isozyme CYP2C9, followed by CYP2C8. These findings indicate that CYP3A5, CYP3A4, CYP2C8 and CYP2C9 play a major role in the transformation of carfentanil to M1 (norcarfentanil), M11, M13 and M15 through N-dealkylation of piperidine ring, hydroxylation of phenethyl group and ketone formation on phenethyl linker by human liver micrsomes.

The opioid epidemic remains a dire public health crisis with millions of people currently suffering from opioid use disorder (OUD) and tens of thousands dying each year. Synthetic opioids are most responsible for the crisis because of their extreme potency and ease of manufacture. Carfentanil for example has an estimated potency 10,000 times greater than morphine and thus is highly dangerous for human use. Herein, we report two synthetic opioid vaccines that elicited high-affinity antibodies against carfentanil and fentanyl with cross-reactivity to other synthetic opioids in mice and offered protection against opioid-induced respiratory depression, the primary cause of overdose deaths. These vaccines also successfully diminished drug biodistribution to the brain and shielded against opioid analgesic effects. Collectively, these findings provide new insights into the development of immunotherapeutic strategies aimed at opioid abuse and overdose.

Health-care workers, laboratorians and overdose prevention centers rely on commercial immunoassays to detect the presence of fentanyl; however, the cross-reactivity of fentanyl analogs with these kits is largely unknown. To address this, we conducted a pilot study evaluating the detection of 30 fentanyl analogs and metabolites by 19 commercially available kits (9 lateral flow assays, 7 heterogeneous immunoassays and 3 homogenous immunoassays). The analogs selected for analysis were compiled from the Drug Enforcement Administration and National Forensic Laboratory Information System reports from 2015 to 2018. In general, the immunoassays tested were able to detect their intended fentanyl analog and some closely related analogs, but more structurally diverse analogs, including 4-methoxy-butyryl fentanyl and 3-methylfentanyl, were not well detected. Carfentanil was only detected by kits specifically designed for its recognition. In general, analogs with group additions to the piperidine, or bulky rings or long alkyl chain modifications in the N-aryl or alkyl amide regions, were poorly detected compared to other types of modifications. This preliminary information is useful for screening diagnostic, forensic and unknown powder samples for the presence of fentanyl analogs and guiding future testing improvements.

Background In the era of highly potent illicit opioids, such as fentanyl and carfentanil, injectable opioid agonist treatment (iOAT) is an effective treatment for those with severe and treatment-refractory opioid use disorder. Untreated opioid use disorder in pregnancy can lead to maternal and neonatal morbidity and mortality. There are currently limited reports on the use of iOAT in pregnant women. The in-patient setting may provide an opportunity to pregnant women for stabilization with iOAT where first line therapies have been ineffective. Case summary We report a case of a pregnant individual who engaged in daily intravenous fentanyl who was admitted to the hospital at 29 weeks gestation for stabilization with iOAT, methadone, and slow-release oral morphine. Before admission, she endured 6 opioid overdoses in her pregnancy and continued to use illicit intravenous opioids in the community despite high dose methadone combined with slow-release oral morphine. Her withdrawal symptoms and cravings were ameliorated with hydromorphone 90 mg IM/IV BID, methadone 135 mg daily, and morphine sulfate sustained release 600 mg daily. With this regimen, she was able to reduce her intravenous fentanyl use to a single episode during her hospitalization. She completed her pregnancy in hospital, delivering a full-term live infant after receiving comprehensive prenatal care. Discussion This case report highlights iOAT as an option during pregnancy and describes the in-patient setting as appropriate to retain high-risk patients in care. This approach may benefit those who are refractory to standard opioid agonist treatment, the numbers of whom may be rising as tolerance to the illicit supply increases.

The opioid epidemic in Ontario has seen opioid-related deaths double in recent years, from 676 deaths in 2014 to 1,474 in 2018, with an overwhelming prevalence of fentanyl and fentanyl-analogues, such as carfentanil. The presence of drug paraphernalia and a history of drug-use is often a strong indicator of a drug-related death, indicating a need for toxicological analysis. Demographic and drug-related patterns associated with opioid deaths in Ontario from June 2017 to December 2018 (n = 2403) were investigated using data collected from the Coroner’s Opioid Investigative Aid (OIA). This work aims to provide insight on how the opioid epidemic affects certain demographics to aid investigators conduct targeted analyses and help public health officials identify vulnerable communities. Chi-square and logistic regressions were conducted to evaluate if age and sex were predictors for the presence of drug paraphernalia, and if drug paraphernalia, sex, age, or history of drug use were associated with causes of deaths (COD). Chi-square analysis revealed that sex (p

Detection of new psychoactive substances and synthetic opioids is generally performed by means of targeted methods in mass spectrometry, as they generally provide adequate sensitivity and specificity. Unfortunately, new and unexpected compounds are continuously introduced in the illegal market of abused drugs, preventing timely updating of the analytical procedures. Moreover, the investigation of biological matrices is influenced by metabolism and excretion, in turn affecting the chance of past intake detectability. In this scenario, new opportunities are offered by both the non-targeted approaches allowed by modern UHPLC-HRMS instrumentation and the investigation of hair as the matrix of choice to detect long-term exposure to toxicologically relevant substances. In this study, we present a comprehensive and validated workflow that combines the use of UHPLC-QTOF-HRMS instrumentation with a simple hair sample extraction procedure for the detection of a variety of fentanyl analogues and metabolites. A simultaneous targeted and untargeted analysis was applied to 100 real samples taken from opiates users. MS and MS/MS data were collected for each sample. Data acquisition included a TOF-MS high-resolution scan combined with TOF-MS/MS acquisition demonstrating considerable capability to detect expected and unexpected substances even at low concentration levels. The predominant diffusion of fentanyl was confirmed by its detection in 68 hair samples. Other prevalent analogues were furanylfentanyl (28 positive samples) and acetylfentanyl (14 positive samples). Carfentanil, methylfentanyl, and ocfentanil were not found in any of the analyzed samples. Furthermore, the retrospective data analysis based on untargeted acquisition allowed the identification of two fentanyl analogues, namely β-hydroxyfentanyl and methoxyacetylfentanyl, which were not originally included in the panel of targeted analytes. Electronic supplementary material The online version of this article (10.1007/s00216-020-02994-x) contains supplementary material, which is available to authorized users.

Because of its remarkable potency and relative ease of synthesis, carfentanil (1) has recently emerged as a problematic contaminant in other drugs of abuse. Carfentanil and its close analogs, currently approved only for large animal veterinary medicine, have found use both as illicit additives to the clandestine manufacture of scheduled drugs and as chemical weapons. In this Review, the background, synthesis, manufacture, metabolism, pharmacology, approved indications, dosage, and adverse effects of carfentanil will be discussed along with its emergence as a key player in the ongoing opioid crisis.

Carfentanil is an ultra-potent opioid with an analgesic potency 10,000 times that of morphine but has received little scientific investigation. Three experiments were conducted to evaluate the toxicity of carfentanil and the efficacy of naloxone in adult male African green monkeys. The first experiment determined the ED50 (found to be 0.71 μg/kg) of subcutaneous carfentanil for inducing bradypnea and/or loss of posture. Experiment 2 attempted to establish the ED50 of naloxone for rapidly reversing the bradypnea/loss of posture induced by carfentanil (1.15 μg/kg). Experiment 3 evaluated the effects of carfentanil (0.575 μg/kg) alone, the safety of naloxone (71-2841 μg/kg), and the efficacy of naloxone (71-710 μg/kg) administration at two time points following carfentanil (1.15 μg/kg) on operant choice reaction time. Collectively, these experiments characterized the temporal progression of carfentanil-induced toxic signs, determined the range of naloxone doses that restored respiratory and gross behavioral function, and determined the time course and range of naloxone doses that partially or completely reversed the effects of carfentanil on operant choice reaction time performance in African green monkeys. These results have practical relevance for the selection of opioid antagonists, initial doses, and expected functional outcomes following treatment of synthetic opioid overdose in a variety of operational/emergency response contexts.

Increased prevalence of illicitly manufactured fentanyl and fentanyl analogs has contributed substantially to overdose deaths in the United States (1-3). On October 26, 2015, CDC issued a Health Advisory regarding rapid increases in deaths involving fentanyl. This CDC Health Advisory has been updated twice to address increases in fentanyl and fentanyl analog overdoses and their co-occurrence with nonopioids (4). Deaths involving carfentanil, an analog reportedly 10,000 times more potent than morphine and 100 times more potent than fentanyl, were first reported in Florida, Michigan, and Ohio in 2016 and described in an August 2016 CDC Health Advisory (1,5). Carfentanil is used to rapidly immobilize large animals in veterinary medicine and has no U.S. approved therapeutic use in humans. Carfentanil's street price per dose is likely lower than that of heroin. During 2016 and 2017, an outbreak of carfentanil-involved fatal overdoses in Florida emerged, and the Medical Examiner jurisdiction serving Sarasota, Manatee, and DeSoto counties (the Sarasota area) was the outbreak epicenter. This report describes toxicology profiles, sociodemographic information, and geographic distributions of carfentanil-involved fatal overdoses (carfentanil deaths) in the Sarasota area compared with those in the rest of Florida (i.e., all Florida counties excluding Sarasota area) from January 2016 to December 2017. The Sarasota area accounted for 19.0% of 1,181 statewide carfentanil deaths that occurred during this time and experienced a peak in carfentanil deaths preceding the larger Florida outbreak. The report of a single carfentanil death from August to December 2017 (compared with 73 reported deaths during the same period in 2016) appeared to mark the end of the outbreak in the area. The threat of such rapid, intense fatal overdose outbreaks highlights the need for accelerated reporting, reliable data sharing systems, and novel proactive surveillance to support targeted prevention and response efforts by public health and safety organizations (6).

Background Rapid identification of fentanyl at the point-of-care is critical. Urine fentanyl concentrations in overdose cases start at single-digit nanograms per milliliter. No fentanyl point-of-care assay with a cutoff at single-digit nanograms per milliliter is available. Methods A competitive lateral flow assay (LFA) was developed using gold nanoparticles and optimized for rapid screening of fentanyl in 5 minutes. Urine samples from 2 cohorts of emergency department (ED) patients were tested using the LFA and LC-MS/MS. The 2 cohorts consisted of 218 consecutive ED patients with urine drug-of-abuse screen orders and 7 ED patients with clinically suspected fentanyl overdose, respectively. Results The LFA detected fentanyl (≥1 ng/mL) and the major metabolite norfentanyl (≥10 ng/mL) with high precision. There was no cross-reactivity with amphetamine, cocaine, morphine, tetrahydrocannabinol, methadone, buprenorphine, naloxone, and acetaminophen at 1000 ng/mL and 0.03%, 0.4%, and 0.05% cross-reactivity with carfentanil, risperidone, and 9-hydroxyrisperidone, respectively. In 218 consecutive ED patients, the prevalence of cases with fentanyl ≥1 ng/mL or norfentanyl ≥10 ng/mL was 5.5%. The clinical sensitivity and specificity of the LFA were 100% (95% CI, 75.8–100%) and 99.5% (95% CI, 97.3–99.9%), respectively. The positive and negative predictive values were 92.3% (95% CI, 66.7–98.6%) and 100% (95% CI, 98.2–100%), respectively. The concordance between the LFA and LC-MS/MS was 100% in the 7 suspected fentanyl overdose cases (5 positive, 2 negative). Conclusions The LFA can detect fentanyl and norfentanyl with high clinical sensitivity and specificity in the ED population with rapid fentanyl screening needs.

Background and Purpose Mitragyna speciosa, more commonly known as kratom, is a plant that contains opioidergic alkaloids but is unregulated in most countries. Kratom is used in the self‐medication of chronic pain and to reduce illicit and prescription opioid dependence. Kratom may be less dangerous than typical opioids because of the stronger preference of kratom alkaloids to induce receptor interaction with G proteins over β‐arrestin proteins. We hypothesized that kratom (alkaloids) can also reduce alcohol intake. Experimental Approach We pharmacologically characterized kratom extracts, kratom alkaloids (mitragynine, 7‐hydroxymitragynine, paynantheine, and speciogynine) and synthetic carfentanil‐amide opioids for their ability to interact with G proteins and β‐arrestin at μ, δ, and κ opioid receptors in vitro. We used C57BL/6 mice to assess to which degree these opioids could reduce alcohol intake and whether they had rewarding properties. Key Results Kratom alkaloids were strongly G protein‐biased at all three opioid receptors and reduced alcohol intake, but kratom and 7‐hydroxymitragynine were rewarding. Several results indicated a key role for δ opioid receptors, including that the synthetic carfentanil‐amide opioid MP102—a G protein‐biased agonist with modest selectivity for δ opioid receptors—reduced alcohol intake, whereas the G protein‐biased μ opioid agonist TRV130 did not. Conclusion and Implications Our results suggest that kratom extracts can decrease alcohol intake but still carry significant risk upon prolonged use. Development of more δ opioid‐selective synthetic opioids may provide a safer option than kratom to treat alcohol use disorder with fewer side effects., ▪

The metabolism of carfentanil was assessed using human, dog, and rat pulmonary microsomes. Mass spectrometry based analysis allowed for metabolite identification and species differentiation. Participation of different metabolic enzymes in carfentanil biotransformation was also assessed. Metabolite profiling was accomplished by incubating 10 µM carfentanil in human, dog, and rat lung microsomes. The metabolites were separated and analyzed by ultra-high performance liquid chromatography/high-resolution mass spectrometry. In total, 18 metabolites were detected. Nine metabolites were authentically identified through comparison to synthesized reference standards. In human lung microsomes, nine metabolites were identified. In dog lung microsomes, 15 metabolites were identified with three being dog specific. In rat lung microsomes, 15 metabolites were identified and two were rat specific. Proposed metabolic pathways included N-dealkylation, monohydroxylation, dihydroxylation, N-oxidation of piperidine ring nitrogen, and ketone formation. Participation of enzymes CYP2B6, CYP2E1, CYP2J2, and CYP3A4/5 to carfentanil metabolism was suggested by selective enzymatic inhibition. The pulmonary clearance in human lung microsomes was lower than the previously reported hepatic metabolism suggesting organ specific metabolic rates. The contribution of multiple cytochrome P450 enzymes to human, dog, and rat pulmonary microsomal carfentanil biotransformation varied between species. The identified metabolites may provide useful markers for possible forensic and clinical determination of the mode of ingestion but the use of dog and rat animal models was not indicated. To our knowledge, this is the first reported use of chemically synthesized reference standards for the unequivocal identification of lung carfentanil metabolites.

Graphical abstract, Highlights • Carfentanil aerosol induced profound cardiorespiratory and physiological effects. • Carfentanil was bioavailable approximately 3 times longer than naloxone. • Naloxone was able to rapidly reverse the effects of a lethal exposure., Carfentanil is a powerful synthetic opioid that is approximately 100 times more potent than fentanyl and 10,000 times more potent than morphine. Carfentanil was originally intended to be used as a sedative for big game animals in a veterinary setting, but it is becoming increasingly recognized as a public health concern. We set out to investigate the effectiveness of naloxone against a potentially lethal dose of inhaled carfentanil in male ferrets. Ferrets were implanted with telemetry devices to study cardiac parameters and exposed to aerosolized carfentanil in a whole-body plethysmography chamber to record respiratory parameters. We observed profound respiratory depression in exposed animals, which led to apneic periods constituting 24-31% of the exposure period. Concomitant with these apneic periods, we also observed cardiac abnormalities in the form of premature junctional contractions (PJCs). At our acute exposure dose, lethal in 3% of our animals, naïve ferrets were unresponsive and incapacitated for a total of 126.1 ± 24.6 minutes. When administered intramuscularly at human equivalent doses (HEDs) of either 5 mg or 10 mg, naloxone significantly reduced the time that ferrets were incapacitated following exposure, although we observed no significant difference in the reduction of time that the animals were incapacitated between the treatment groups. Naloxone was able to quickly resolve the respiratory depression, significantly reducing the frequency of apneic periods in carfentanil-exposed ferrets. Our results suggest that naloxone, when administered via intramuscular injection following incapacitation, is a viable treatment against the effects of a potentially lethal dose of inhaled carfentanil.

To combat the ongoing opioid epidemic, our laboratory has developed and evaluated an approach to detect fentanyl analogs in urine and plasma by screening LC-QTOF MS/MS spectra for ions that are diagnostic of the core fentanyl structure. MS/MS data from a training set of 142 fentanyl analogs were used to select the four product ions and six neutral losses that together provided the most complete coverage (97.2%) of the training set compounds. Furthermore, using the diagnostic ion screen against a set of 49 fentanyl analogs not in the training set resulted in 95.9% coverage of those compounds. With this approach, lower reportable limits for fentanyl and a subset of fentanyl-related compounds range from 0.25 to 2.5 ng/mL in urine and 0.5 to 5.0 ng/mL in plasma. This innovative processing method was applied to evaluate simulated exposure samples of remifentanil and carfentanil in water and their metabolites remifentanil acid and norcarfentanil in urine. This flexible approach enables a way to detect emerging fentanyl analogs in clinical samples.

Hospital samples collected in gel separator tubes are often submitted to forensic toxicology laboratories for analysis in impaired driving and death investigations. Drug adsorption to the gel separator material may lead to underestimation of the drug concentration present at the time of sample collection, potentially affecting the interpretation of analytical results. Using liquid chromatography--tandem mass spectrometry (LC--MS-MS), decreases in plasma concentration of 53 drugs and metabolites relevant to forensic toxicology casework were investigated in samples stored in BD Vacutainer® PSTTM tubes for up to 3 months. After storage for only 1 day, approximately 50% of the drugs and metabolites had significantly lower concentrations in plasma separation tubes (PSTs) compared to non-gel tubes (up to 27% lower). After storage for 3 months, approximately 75% of the drugs and metabolites had significantly lower concentrations in PSTs compared to non-gel tubes (up to 69% lower). Fentanyl, carfentanil, ketamine, diphenhydramine and several antidepressants were among the drugs most susceptible to adsorption. Central nervous system stimulants (e.g., methamphetamine and amphetamine) as well as naturally-occurring and semi-synthetic opioids (e.g., morphine, hydromorphone and oxycodone) were among the drugs least susceptible to adsorption and displayed only minimal relative decreases in concentration (if any) over the 3-month sample storage period. The potential for decreases in drug concentration due to adsorption of drugs to the gel material should be considered for toxicological interpretation based on the analysis of a sample collected in a gel separator tube.

The endogenous mu-opioid receptor (MOR) system modulates a multitude of social and reward-related functions, and exogenous opiates also influence sex drive in humans and animals. Sex drive shows substantial variation across humans, and it is possible that individual differences in MOR availability underlie interindividual of variation in human sex drive. We measured healthy male subjects’ (n = 52) brain’s MOR availability with positron emission tomography (PET) using an agonist radioligand, [11C]carfentanil, that has high affinity for MORs. Sex drive was measured using self-reports of engaging in sexual behaviour (sex with partner and masturbating). Bayesian hierarchical regression analysis revealed that sex drive was positively associated with MOR availability in cortical and subcortical areas, notably in caudate nucleus, hippocampus, and cingulate cortices. These results were replicated in full-volume GLM analysis. These widespread effects are in line with high spatial autocorrelation in MOR expression in human brain. Complementary voxel-based morphometry analysis (n = 108) of anatomical MR images provided limited evidence for positive association between sex drive and cortical density in the midcingulate cortex. We conclude that endogenous MOR tone is associated with individual differences in sex drive in human males.

Eating behavior varies greatly between individuals, but the neurobiological basis of these trait-like differences in feeding remains poorly understood. Central μ-opioid receptors (MOR) and cannabinoid CB1 receptors (CB1R) regulate energy balance via multiple neural pathways, promoting food intake and reward. Because obesity and eating disorders have been associated with alterations in the brain’s opioid and endocannabinoid signaling, the variation in MOR and CB1R system function could potentially underlie distinct eating behavior phenotypes. In this retrospective positron emission tomography (PET) study, we analyzed [11C]carfentanil PET scans of MORs from 92 healthy subjects (70 males and 22 females), and [18F]FMPEP-d2 scans of CB1Rs from 35 subjects (all males, all also included in the [11C]carfentanil sample). Eating styles were measured with the Dutch Eating Behavior Questionnaire (DEBQ). We found that lower cerebral MOR availability was associated with increased external eating—individuals with low MORs reported being more likely to eat in response to environment’s palatable food cues. CB1R availability was associated with multiple eating behavior traits. We conclude that although MORs and CB1Rs overlap anatomically in brain regions regulating food reward, they have distinct roles in mediating individual feeding patterns. Central MOR system might provide a pharmacological target for reducing individual’s excessive cue-reactive eating behavior.

A case is described where a property was used as a clandestine opioid (fentanyl and carfentanil) processing, handling, pill pressing, and packaging site. These activities resulted in potentially lethal opioid residue contamination which remained after police intervention. This case details the environmental assessment and sampling procedures, findings, and decontamination processes that were used to mitigate the property. A safe re-occupancy criterion was established and used as the basis for adoption of a state standard for residential cleanup in California. Regulatory hurdles and key lessons are presented so that others may consider development of similar public health policy. Involvement of public health departments in the assessment and cleanup of sites contaminated with opioids and other illicit drugs and the development of standards for cleanup and worker protection is an important and yet often overlooked public health measure.

Summary Today, NPS are increasingly being related to post-mortem cases, and this problem drastically intensifies as a result of the New Synthetic Opioids (NSOs) surge. Among NSOs, carfentanil (CaF) is the most potent fentanyl analogue and was central to a large number of NSOs-related fatalities in North America, as well as in UE, since 2016. In this worrisome context, this manuscript reports the first CaF-related fatality occurred in France. A 41-years-old man was found dead with a syringe planted under his tongue. This man has a psychiatric follow-up for opiate addiction and his recent medical history included intoxication with fentanyl derivatives. Toxicological investigations of post-mortem samples (blood, urine and hair), and syringe were requested. CaF (with several other psychoactive drugs at non-toxic level) was detected in biological samples and in syringe residue using LC-HRMS, and quantified using LC-MS/MS in blood, urine and hair (from proximal to distal hair section – 3 cm length each) at 4.20, 0.40 μg/L and 54/114/166 pg/mg, respectively. The relatively high post-mortem CaF blood concentration together with the absence of metabolite (especially NorCaF) suggests a sudden death of the victim immediately following a significant CaF dose intake (presumably injected) that can explain the decease.

Excessive sucrose consumption elicits addiction-like craving that may underpin the obesity epidemic. Opioids and dopamine mediate the rewarding effects of drugs of abuse, and of natural rewards from stimuli such as palatable food. We investigated the effects of sucrose using PET imaging with [11C]carfentanil (μ-opioid receptor agonist) and [11C]raclopride (dopamine D2/3 receptor antagonist) in seven female anesthetized Göttingen minipigs. We then gave minipigs access to sucrose solution for one hour on 12 consecutive days and performed imaging again 24 hours after the final sucrose access. In a smaller sample of five minipigs, we performed an additional [11C]carfentanil PET session after the first sucrose exposure. We calculated voxel-wise binding potentials (BPND) using the cerebellum as a region of non-displaceable binding, analyzed differences with statistical non-parametric mapping, and performed a regional analysis. After 12 days of sucrose access, BPND of both tracers had declined significantly in striatum, nucleus accumbens, thalamus, amygdala, cingulate cortex and prefrontal cortex, consistent with down-regulation of receptor densities. After a single exposure to sucrose, we found decreased binding of [11C]carfentanil in nucleus accumbens and cingulate cortex, consistent with opioid release. The lower availability of opioid and dopamine receptors may explain the addictive potential associated with intake of sucrose.

[Image: see text] Carfentanil is a synthetic opioid significantly more potent than clinically prescribed fentanyl. The primary metabolites of carfentanil, generated from human liver microsomes, were structurally confirmed through chemical synthesis. The synthesized compounds were evaluated for μ-opioid receptor (MOR) functional activity. Of the six metabolites assayed, a major metabolite showed comparable activity to the parent opioid. Three other metabolites showed significant MOR functional activity. The availability of the metabolites could aid improvements in the analysis of biomedical samples obtained from suspected human exposures to carfentanil and development of treatment protocols.

KEY POINTS In 2018, at least 4460 Canadians died from an opioid overdose, of which 94% were determined to be unintentional (accidental) overdoses. This represents a 9% increase in overdose deaths from 2017 and a 48% increase from 2016.[1][1] The recent emergence of street fentanyl, carfentanil and

Background Conducted in Dayton, Ohio, the study aims to characterize user knowledge and experiences with non-pharmaceutical fentanyl-type drugs (NPFs) and compare self-reports with urine toxicology for NPFs and heroin. Methods Between May 2017–January 2018, 60 individuals who self-reported heroin/NPF use were interviewed using structured questionnaire on socio-demographics, NPF and other drug use practices. Unobserved urine samples were collected and analyzed using: 1) liquid-chromatography-tandem mass spectrometry (LC–MS/MS)-based method (Toxicology lab) to identify 34 fentanyl analogues, metabolites, and other synthetic opioids; 2) immunoassay-based method to screen for opiates (heroin). Sensitivity, specificity and Cohen’s kappa were calculated to assess agreement between self-reports and urine toxicology. Results The sample was 52% female, and over 90% white. Almost 60% reported preference for heroin, and 40% for NPF. Participants endorsed a number of ways of distinguishing heroin from NPF, including appearance (88.3%), effects (76.7%), taste (55%), and information provided by dealers (53.3%). Almost 80% felt confident they could distinguish heroin from NPF, but knowledge about fentanyl analogues was limited. LC–MS/MS testing identified 8 types of NPFs. Over 88% tested positive for NPFs, including 86% fentanyl, 48% carfentanil, 42% acetyl fentanyl. About 47% screened positive for opiates/heroin, and all of them were also positive for NPFs. When comparing self-reported use of NPF to urine toxicology, sensitivity and specificity were relatively high (84% and 83.3%, accordingly), while Cohen’s Kappa was 0.445, indicating fair agreement. Sensitivity and specificity were lower for heroin (77.8% and 50.0%, accordingly), and Cohen’s Kappa was 0.296, indicating low agreement between self-reports of heroin use and urine toxicology. Discussion Nearly 90% of the study participants tested positive for NPF-type drugs. Participants were more likely to over-report heroin use and underreport NPF use. The majority had little knowledge about fentanyl analogues. Study findings will inform development of novel harm reduction approaches to reduce overdose mortality.

Opioid abuse in the United States has been declared a national crisis and is exacerbated by an inexpensive, readily available, and illicit supply of synthetic opioids. Specifically, fentanyl and related analogues such as carfentanil pose a significant danger to opioid users due to their high potency and rapid acting depression of respiration. In recent years these synthetic opioids have become the number one cause of drug-related deaths. In our research efforts to combat the public health threat posed by synthetic opioids, we have developed monoclonal antibodies (mAbs) against the fentanyl class of drugs. The mAbs were generated in hybridomas derived from mice vaccinated with a fentanyl conjugate vaccine. Guided by a surface plasmon resonance (SPR) binding assay, we selected six hybridomas that produced mAbs with 10(−11) M binding affinity for fentanyl, yet broad cross-reactivity with related fentanyl analogues. In mouse antinociception models, our lead mAb (6A4) could blunt the effects of both fentanyl and carfentanil in a dose-responsive manner. Additionally, mice pretreated with 6A4 displayed enhanced survival when subjected to fentanyl above LD(50) doses. Pharmacokinetic analysis revealed that the antibody sequesters large amounts of these drugs in the blood, thus reducing drug biodistribution to the brain and other tissue. Lastly, the 6A4 mAb could effectively reverse fentanyl/carfentanil-induced antinociception comparable to the opioid antagonist naloxone, the standard of care drug for treating opioid overdose. While naloxone is known for its short half-life, we found the half-life of 6A4 to be approximately 6 days in mice, thus monoclonal antibodies could theoretically be useful in preventing renarcotization events in which opioid intoxication recurs following quick metabolism of naloxone. Our results as a whole demonstrate that monoclonal antibodies could be a desirable treatment modality for synthetic opioid overdose and possibly opioid use disorder.

Since the early 2010s, deaths due to the use of new synthetic opioids (NSO) including fentanyl and its analogs have been increasing dramatically. As fentanyl analogs bear strong structural similarities, they can share common metabolites. In some clinical or forensic cases, it can be important to demonstrate the presence of both the metabolite and the parent product to confirm that the compound is responsible for the intoxication. Norcarfentanil is a common metabolite of carfentanil (NSO) and remifentanil (widely used in medical care). This article reported the investigation of norcarfentanil origin in three cases. Comprehensive screenings were performed using gas chromatography coupled to mass spectrometry and liquid chromatography coupled to a diode array detection, whereas targeted screening of NSO were performed using liquid chromatography coupled to tandem mass spectrometry. Norcarfentanil was detected at concentrations ranging from 0.05 to 15.8 ng/mL in plasma and from 8.8 to 1820 ng/mL in urine, but carfentanil was detected in two out of the three cases. The presence of norcarfentanil has been supposed to be due to the treatment with remifentanil during the medical care of the patient. In the first two cases, norcarfentanil was present as the metabolite of carfentanil, whereas in the last case, norcarfentanil was the metabolite of remifentanil. Without the identification of remifentanil, confusion could occur, and norcarfentanil could be attributed to carfentanil misuse.

INTRODUCTION: There is a lack of information on illicitly manufactured fentanyl and fentanyl analogue-related (IMF) unintentional overdose death trends over time. The study analyzes IMF-related unintentional overdose fatalities that occurred between July 2015 and June 2017 in Montgomery County, Ohio, an area with the highest rates of unintentional overdose mortality in Ohio. METHODS: LC-MS/MS-based method was used to identify fentanyl analogs and metabolites in 724 unintentional overdose death cases. The Chi-square statistic was used to assess differences over time in demographic and drug-related characteristics. RESULTS: The number of unintentional overdose death cases testing positive for IMFs increased by 377% between second half of 2015 and first half of 2017. The majority of decedents were white (82.5%) and male (67.8%). The proportion of fentanyl-only (no other analogs) cases declined from 89.2% to 24.6% (p

Nasal spray formulations of naloxone, a mu-opioid receptor (MOR) antagonist, are currently used for the treatment of opioid overdose. They may have additional therapeutic utility also in the absence of opioid agonist drugs, but the onset and duration of action at brain MORs have been inadequately characterized to allow such projections. This study provides initial characterization of brain MOR availability at high temporal resolution following intranasal (IN) naloxone administration to healthy volunteers in the absence of a competing opioid agonist. Fourteen participants were scanned twice using positron emission tomography (PET) and [(11)C]carfentanil, a selective MOR agonist radioligand. Concentrations of naloxone in plasma and MOR availability (relative to placebo) were monitored from 0 to 60 min and at 300–360 min post naloxone. Naloxone plasma concentrations peaked at ~20 min post naloxone, associated with slightly delayed development of brain MOR occupancy (half of peak occupancy reached at ~10 min). Estimated peak occupancies were 67 and 85% following 2 and 4 mg IN doses, respectively. The estimated half-life of occupancy disappearance was ~100 min. The rapid onset of brain MOR occupancy by IN naloxone, evidenced by the rapid onset of its action in opioid overdose victims, was directly documented in humans for the first time. The employed high temporal-resolution PET method establishes a model that can be used to predict brain MOR occupancy from plasma naloxone concentrations. IN naloxone may have therapeutic utility in various addictions where brain opioid receptors are implicated, such as gambling disorder and alcohol use disorder.

Illegal drugs are among the multitude of goods examined by customs officers at the border. With the emergence of fentanyl and fentanyl analogues, the goal of field detection of drugs becomes two-fold: to interdict illegal drug movement and to assist in the protection of the health and safety of frontline officers. This work reports a study of nine fentanyl-related substances (acetylfentanyl, benzoylfentanyl, beta-hydroxythiofentanyl, butyrylfentanyl, carfentanil, despropionylfentanyl, fentanyl, furanylfentanyl and parafluoroisobutyrylfentanyl) using a commercial off-the-shelf ion mobility spectrometer (COTS IMS) and the results from analyzing 84 seized samples containing fentanyl-related substances. The results showed that the COTS IMS was capable of detecting the presence of programmed fentanyl-related substances. Unprogrammed fentanyl-related substances were detected, however no alarm was generated and the information was accessible via the advanced user mode only. The COTS IMS was not able to distinguish between several pairs of substances with similar reduced mobility values. During this study, six fentanyl analogues were intercepted by our laboratory for the first time (2-isopropylfuranylfentanyl, 2-methoxyfuranylfentanyl, 2-methfuranylfentanyl, 4-chlorofuranylfentanyl, cyclopropylfentanyl and methoxyacetylfentanyl) and their reduced mobility values are presented herein.

Carfentanil is a synthetic fentanyl analogue approved for veterinary use. It is a mu-opioid receptor agonist with an estimated analgesic potency approximately 10,000 times that of morphine and 20-30 times that of fentanyl, based on animal studies. Since 2016, an increasing number of reports describe detection of carfentanil in the illicit drug supply. Little is known about the pharmacology of carfentanil in humans. Its high potency and presumed high lipophilicity, large volume of distribution, and potential active metabolites have raised concerns about the management of people exposed to carfentanil as well as the safety of first responders. Exposed individuals exhibit features of an opioid toxidrome and respond to opioid antagonists such as naloxone, although empiric dose requirements are unknown and very high doses may be required. Rare reports of suspected accidental poisoning of first responders have not been analytically confirmed and are unlikely to represent true poisoning. General occupational hygiene measures, including regular decontamination with soap and water, basic personal protective equipment (nitrile gloves, N95 mask, and eye goggles), and ready access to naloxone are generally sufficient in most circumstances.

Aim Methamphetamine use has increased among individuals with opioid use disorder. The key aims of this study are to detail and contextualise lay knowledge, attitudes, and behaviours related to methamphetamine use in relation to opioid overdose risks in an area dominated by non-pharmaceutical fentanyl-type drugs (NPF). Methods The study recruited 41 individuals in Dayton, Ohio, who reported past 30-day use of methamphetamine and heroin/fentanyl. Interviews included structured and qualitative questions. Urine toxicology analysis was conducted to identify NPFs and other drugs. Open-ended interview sections were audio-recorded, transcribed, and analysed qualitatively using NVivo. Results The mean age was 38.3 years, 51% were female, and 100% non-Hispanic white. Participants described an exceedingly unpredictable local opioid market that became saturated with NPFs. The sample tested positive for 10 NPFs, including fentanyl (100%), acetyl fentanyl (61%), tetrahydrofuran fentanyl (29%), and carfentanil (12%). Most participants believed that methamphetamine could help prevent and/or reverse an opioid-related overdose. Nearly half had personally used it to help manage overdose risks related to NPF. These beliefs were embedded in a lay understanding of how methamphetamine works to stimulate the cardiovascular system. They were acted upon in the context of last resort situations that were determined by a lack of immediate access to naloxone, ambiguities surrounding overdose symptomatology, and easy access to plentiful and inexpensive methamphetamine. Conclusion Lay efforts to rely on methamphetamine to manage NPF-related overdose risks highlight the need for a continuing expansion of take-home-naloxone programs and implementation of other novel harm reduction approaches in communities affected by NPFs.

The detection of fentanyl (FEN) and FEN analogs has been widely communicated throughout the scientific community. While most of the reporting has been in relation to overdose deaths, these drugs are commonly detected in impaired driving cases. A retrospective study of impaired driving cases analyzed between 2017 and 2019 produced 270 cases positive for FEN, carfentanil (CFEN) and/or acetylfentanyl (AFEN). FEN was the predominant drug found in these 270 cases (65.5%) with concentrations ranging from less than 1.0 to 64 ng/mL. CFEN was found alone in 6.6% cases with three concentrations above 1.0 ng/mL. AFEN was always found when FEN was positive with concentrations ranging from

Bariatric surgery is the most effective method for weight loss in morbid obesity. There is significant individual variability in the weight loss outcomes, yet factors leading to postoperative weight loss or weight regain remain elusive. Alterations in the μ-opioid receptor (MOR) and dopamine D2 receptor (D2R) systems are associated with obesity and appetite control, and the magnitude of initial brain receptor system perturbation may predict long-term surgical weight loss outcomes. We tested this hypothesis by studying 19 morbidly obese women (mean BMI 40) scheduled to undergo bariatric surgery. We measured their preoperative MOR and D2R availabilities using positron emission tomography with [11C]carfentanil and [11C]raclopride, respectively, and then assessed their weight development association with regional MOR and D2R availabilities at 24-month follow-up. MOR availability in the amygdala consistently predicted weight development throughout the follow-up period, but no associations were found for D2R. This is the first study to our knowledge to demonstrate that neuroreceptor markers prior to bariatric surgery are associated with postoperative weight development. Postoperative weight regain may derive from dysfunction in the opioid system, and weight loss outcomes after bariatric surgery may be partially predicted based on preoperative brain receptor availability, opening up new potential for treatment possibilities.

The endogenous mu-opioid receptor (MOR) system modulates a multitude of social and reward-related functions, and exogenous opiates also influence sex drive in humans and animals. Sex drive shows substantial variation across humans, and it is possible that individual differences in MOR availability underlie interindividual of variation in human sex drive. Here we measured healthy male subjects’ (n=52) brain’s MOR availability with positron emission tomography (PET) using an agonist radioligand, [11C]carfentanil, that has high affinity for MORs. Sex drive was measured using self-reports of engaging in sexual behaviour (sex with partner and masturbating). Bayesian hierarchical regression analysis revealed that sex drive was positively associated with MOR availability in cortical and subcortical areas, notably in caudate nucleus, hippocampus, and cingulate cortices. These results were replicated in full-volume GLM analysis. These widespread effects are in line with high spatial autocorrelation in MOR expression in human brain. Complementary voxel-based morphometry analysis (n=108) provided limited evidence for association between sex drive and cortical density in the midcingulate cortex. We conclude that endogenous MOR tone is associated with individual differences in sex drive in human males.

Opioids, including the highly potent synthetic opioids fentanyl and carfentanil, are commonly sold on illicit cryptomarkets or Tor darknet markets. Data collected throughout 2019 from 12 large darknet markets that sold opioids enabled observation of the impact of law enforcement seizures and voluntary or scam market closures on the availability of fentanyl and other opioids. Trends in opioid and fentanyl availability before and after law enforcement interventions indicate whether market operators and sellers are deterred and whether market closures lead to displacement, dispersal or substitution. Evidence of all of these outcomes was present in both descriptive and trend analyses, although most effects were short lived. Market closures, especially law enforcement seizures, reduced the availability of opioids, in particular fentanyl, as well as increasing prices and displacing vendors to other markets. Market closures also led vendors to substitute fentanyl for other opioids or other illicit drugs.

Fentanyl analogs continue to play a major role in proliferating the opioid epidemic in the USA. With high rates of overdose deaths, forensic laboratories experience backlogs, which may lead to false-negative results due to drug instability. To address this issue, a quantitative method was validated for fentanyl analogs (3-methylfentanyl, 4-anilino-N-phenethylpiperidine (4-ANPP), 4-fluoro-isobutyrylfentanyl (4-FIBF), acetylfentanyl, acrylfentanyl, butyrylfentanyl, carfentanil, cyclopropylfentanyl, fentanyl, furanylfentanyl, methoxyacetylfentanyl, p-fluorofentanyl and valerylfentanyl) in blood using liquid chromatography–quadrupole-time-of-flight mass spectrometry (LC–QTOF-MS) and used to assess long-term stability under various temperature conditions (–20°C, 4°C, ∼25°C and 35°C) for 9 months. Authentic specimens were also analyzed 6 months apart for applicability to postmortem blood. Method validation resulted in calibration ranges of 1–100 ng/mL and limits of detection of 0.5 ng/mL. Precision and bias were acceptable (within ±7.2% coefficient of variation (CV) and ±15.2%, respectively). Matrix effects exhibited ion enhancement for all analytes, except carfentanil and 4-ANPP in low-quality control (>25%). For long-term stability, fentanyl analogs (except acrylfentanyl) remained stable under room temperature and refrigerated conditions at low and high concentrations (81.3–112.5% target) for 9 months. While most fentanyl analogs remained stable frozen, degradation was observed after 2 weeks (four freeze/thaw cycles). At elevated temperatures, most analytes were stable for 1 week (74.2–112.6% target). Acrylfentanyl was unstable after 24 h under elevated (70% loss) and room temperatures (53–60% loss), 48–72 h when refrigerated (28–40% loss) and 4 weeks when frozen (22% loss). In authentic bloods (n = 7), initial furanylfentanyl (FuF) and 4-ANPP concentrations were 1.1–3.6 and 1.4–6.4 ng/mL, respectively. Percentage loss of FuF and 4-ANPP over 6 months were 16.3–37.4% and 0.2–26.8%, respectively. Samples suspected to contain fentanyl analogs are recommended to be stored refrigerated or frozen with limited freeze/thaw cycles. Due to instability, in the event of an acrylfentanyl overdose, samples should be analyzed immediately or stored frozen with analysis within 1 month.

BackgroundBariatric surgery is the most effective method for weight loss in morbid obesity. There is significant individual variability in the weight loss outcomes, yet factors leading to postoperative weight loss or weight regain remain elusive. Alterations in the µ-opioid receptor (MOR) and dopamine D2 receptor (D2R) systems are associated with obesity, appetite control, and reward processing. The magnitude of initial brain receptor system perturbation is a plausible predictor of long-term surgical weight loss outcomes. The aim was to test this hypothesis by measuring obese subjects’ MOR and D2R availability with positron emission tomography (PET) preoperatively before bariatric surgery and then assessing their weight development association with regional MOR and D2R availabilities at 2-year follow-up.MethodsWe studied 19 morbidly obese women (mean BMI 40, mean age 43) scheduled to undergo bariatric surgery, i.e. Roux-en-Y gastric bypass or sleeve gastrectomy, according to their standard clinical treatment. Preoperative MOR and D2R availabilities were measured using PET with [11C]carfentanil and [11C]raclopride, respectively. Subject weight was recorded at 3, 6, 12, and 24 months after surgery. Radiotracer binding potentials (BPND) were extracted and correlated with patient weight at different time points. ROIs were delineated in the striatum and in limbic and paralimbic components of the emotion and reward networks.ResultsMOR availabilities were not correlated with preoperative weight. MOR availabilities in the amygdala (r = −0.54), insula (r = −0.46), ventral striatum (r = −0.48) and putamen (r = −0.49) were associated with subject weight at 3 months. Significant association was found in the amygdala at 6 months (r = −0.53), 12 (r = −0.49), and 24 months (r = −0.50). D2R availabilities were associated with neither preoperative weight nor weight loss at any follow-up time point.ConclusionsTo our knowledge, this is the first study to demonstrate that neuroreceptor markers prior to bariatric surgery in patients with morbid obesity are associated with the postoperative weight loss. Preoperative MOR availability in the amygdala was associated with long-term postoperative weight development after surgery suggesting that postoperative weight regain may derive from dysfunction in the opioid system. Postoperative weight loss outcomes after bariatric surgery may be partially predicted based on preoperative receptor availability opening up new potential for treatment possibilities.Clinical Trials RegistrationSleevePET2, NCT01373892, http://www.clinicaltrials.gov

The US is in the midst of a major drug epidemic fueled in large part by the widespread recreational use of synthetic opioids such as fentanyl. Persons with opioid use disorder are at significant risk for transmission of injection-associated infections such as hepatitis B virus (HBV) and hepatitis C virus (HCV). Commonly abused substances may antagonize immune responses and promote viral replication. However, the impact of synthetic opioids on virus replication has not been well explored. Thus, we evaluated the impact of fentanyl and carfentanil using in vitro systems that replicate infectious viruses. Fentanyl was used in cell lines replicating HBV or HCV at concentrations of 1 ng, 100 ng, and 10 ug. Viral protein synthesis was quantified by ELISA, while apoptosis and cell death were measured by M30 or MTT assays, respectively. HCV replicative fitness was evaluated in a luciferase-based system. RNAseq was performed to evaluate cellular gene regulation in the presence of fentanyl. Low dose fentanyl had no impact on HCV replication in Huh7.5JFH1 hepatocytes; however, higher doses significantly enhanced HCV replication. Similarly, a dose-dependent increase in HCV replicative fitness was observed in the presence of fentanyl. In the HepG2.2.15 hepatocyte cell line, fentanyl caused a dose-dependent increase in HBV replication, although only a higher doses than for HCV. Addition of fentanyl resulted in significant apoptosis in both hepatocyte cell lines. Cell death was minimal at low drug concentrations. RNAseq identified a number of hepatocyte genes that were differentially regulated by fentanyl, including those related to apoptosis, the antiviral / interferon response, chemokine signaling, and NFκB signaling. Collectively, these data suggest that synthetic opioids promote viral replication but may have distinct effects depending on the drug dose and the viral target. As higher viral loads are associated with pathogenesis and virus transmission, additional research is essential to an enhanced understanding of opioid-virus pathogenesis and for the development of new and optimized treatment strategies.

There has been an alarming increase of novel synthetic opioids (NSOs) in the illegal drug market since 2016. These substances are still detected in forensic case investigations in biological samples as well as in seized materials. Although NSOs are steadily emerging, other potent “old” synthetic opioids are still circulating and involved in fatal overdose cases. This is the case of the potent designer drugs carfentanil and 3-methylfentanyl. These drugs were associated with several deaths since at least 20 years ago, and they are still a public health threat. In this study, we presented postmortem (PM) forensic cases that were positive for carfentanil or 3-methylfentanyl over a four-year period 2017–2020. Quantitative confirmation was via a quantitative liquid chromatography tandem mass spectrometry (LC-MS/MS)-based method that targets 21 designer opioids, able to differentiate isomers such as cis- and trans-3-methylfentanyl, with a limit of quantification of 0.05 ng/mL. A total of 1136 and 153 PM cases were received in the laboratory from different regions of the United States positive for carfentanil and 3-methylfentanyl, respectively. PM peripheral blood ranged from 0.050‒32 ng/mL for carfentanil, and 0.057‒7.2 and 0.057‒2.2 ng/mL for cis- and trans-3-methylfentanil, respectively. During this period, fentanyl was the most common concomitant drug detected within these cases. Heroin and cocaine were also highly prevalent in those cases positive for carfentanil. Other NSOs such as 2-furanylfentanyl, cyclopropylfentanyl and para-fluorobutyrylfentanyl were also significant findings in positive carfentanil cases. For 3-methylfentanyl, cocaine was the second most prevalent co-occurrence drug, while heroin decreased over the years in those cases where 3-methylfentanyl was confirmed.

An analysis of fentanyl analog exposures in Cook County, Illinois recently published in this journal by Chhabra et al. found that more than half of urine drug screens detected at least one fentanyl...

Eating behavior varies greatly between healthy individuals, but the neurobiological basis of these trait-like differences in feeding remains unknown. Central µ-opioid receptors (MOR) and cannabinoid CB1-receptors (CB1R) regulate energy balance via multiple neural pathways, promoting food intake and reward. Because obesity and eating disorders have been associated with alterations in the brain’s opioid and endocannabinoid signaling, the variation in MOR and CB1R system function could potentially underlie distinct eating behavior phenotypes. In this retrospective positron emission tomography (PET) study, we analyzed [11C]carfentanil PET scans of MORs from 92 healthy subjects (70 males and 22 females), and [18F]FMPEP-d2 scans of CB1Rs from 35 subjects (all males, all also included in the [11C]carfentanil sample). Eating styles were measured with the Dutch Eating Behavior Questionnaire (DEBQ). We found that lower cerebral MOR availability was associated with increased external eating – individuals with low MORs reported being more likely to eat in response to environment’s palatable food cues. CB1R availability was associated with multiple eating behavior traits. We conclude that although MORs and CB1Rs overlap anatomically and functionally in the brain, they have distinct roles in mediating individual feeding patterns.

Carfentanil is a synthetic opioid restricted to veterinary use due to its potency. Public health concerns have been raised as to the potential of carfentanil to exhibit toxicity after absorption via the percutaneous route following unintentional contamination. The current study measured the penetration of free base carfentanil through human, pig and rat skin using in vitro static diffusion cells. The human penetration rates were compared against literature toxicology values and indicated that, dependent on the contamination density, contamination area and residence time, skin decontamination and medical countermeasures may be required to ameliorate toxicity. The pig and rat skin penetration data will form the basis of future work to develop relevant in silico and in vivo models to further elucidate likely toxic effects and the medical strategies to mitigate against them.

Background A significant number of deaths caused by opioids involve fentanyl and/or one of its very potent analogs (e.g., carfentanil). Some clinical reports suggest larger doses of opioid receptor antagonists may be required to reverse the effects of carfentanil compared with other opioid receptor agonists, although this has not been examined extensively in vivo. The current study compared the discriminative stimulus effects of fentanyl, carfentanil, and heroin, and their antagonism by naltrexone. Methods Eight male Sprague-Dawley rats were trained to discriminate 10.0 μg/kg fentanyl from saline while responding under a fixed-ratio 10 schedule of food presentation. Dose-effect curves were determined for the opioid receptor agonists fentanyl (1.0–32.0 μg/kg), carfentanil (0.1–3.2 μg/kg), and heroin (10.0–320.0 μg/kg), then redetermined following a 15-minute pretreatment with 0.1 mg/kg naltrexone. Results Fentanyl, carfentanil, and heroin dose-dependently increased responding on the fentanyl-associated lever and decreased the rate of lever pressing. Carfentanil and heroin were approximately 10-fold more and less potent, respectively, than fentanyl at eliciting >80 % responding on the fentanyl-associated lever. Pretreatment with 0.1 mg/kg naltrexone resulted in a significant rightward shift in the fentanyl and heroin but not carfentanil dose-effect curves. Conclusions Differences in the effectiveness of naltrexone to attenuate the discriminative stimulus effects of carfentanil, compared with fentanyl and heroin, suggest that there may be differences in how carfentanil exerts its discriminative stimulus effects compared with other opioids. Further evaluation is needed of potential pharmacological and behavioral differences between carfentanil and other opioids, particularly in the context of toxicity.

Active immunization is an emerging potential modality to combat fatal overdose amid the opioid epidemic. In this study, we described the design, synthesis, formulation, and animal testing of an efficacious vaccine against fentanyl. The vaccine formulation is composed of a novel fentanyl hapten conjugated to tetanus toxoid (TT) and adjuvanted with liposomes containing monophosphoryl lipid A adsorbed on aluminum hydroxide. The linker and hapten N-phenyl-N-(1-(4-(3-(tritylthio)propanamido)phenethyl)piperidin-4-yl)propionamide were conjugated sequentially to TT using amine-N-hydroxysuccinimide-ester and thiol–maleimide reaction chemistries, respectively. Conjugation was facile, efficient, and reproducible with a protein recovery of >98% and a hapten density of 30–35 per carrier protein molecule. In mice, immunization induced high and robust antibody endpoint titers in the order of >106 against the hapten. The antisera bound fentanyl, carfentanil, cyclopropyl fentanyl, para-fluorofentanyl, and furanyl fentanyl in vitro with antibody-drug dissociation constants in the range of 0.36–4.66 nM. No cross-reactivity to naloxone, naltrexone, methadone, or buprenorphine was observed. In vivo, immunization shifted the antinociceptive dose–response curve of fentanyl to higher doses. Collectively, these preclinical results showcased the desired traits of a potential vaccine against fentanyl and demonstrated the feasibility of immunization to combat fentanyl-induced effects.