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

Recent Scaffold Hopping Applications in Central Nervous System Drug Discovery

The concept of bioisosterism and the implementation of bioisosteric replacement is fundamental to medicinal chemistry. The exploration of bioisosteres is often used to probe key structural features of candidate pharmacophores and enhance pharmacokinetic properties. As the understanding of bioisosterism has evolved, capabilities to undertake more ambitious bioisosteric replacements have emerged. Scaffold hopping is a broadly used term in the literature referring to a variety of different bioisosteric replacement strategies, ranging from simple heterocyclic replacements to topological structural overhauls. In this work, we have highlighted recent applications of scaffold hopping in the central nervous system drug discovery space. While we have highlighted the benefits of using scaffold hopping approaches in central nervous system drug discovery, these are also widely applicable to other medicinal chemistry fields. We also recommend a shift toward the use of more refined and meaningful terminology within the realm of scaffold hopping.

Knowledge, attitudes, and behaviors related to the fentanyl-adulterated drug supply among people who use drugs in Oregon

INTRODUCTION

Nonpharmaceutical fentanyl has reconfigured the U.S. illicit drug market, contributing to a drastic increase in overdose drug deaths. While illicit fentanyl has subsumed the drug supply in the Northeast and Midwest, it has more recently reached the West. For this study, we explored knowledge, attitudes, and behaviors among people who use drugs in Oregon in the context of the emergence of fentanyl in the drug supply.

METHODS

We conducted in-depth interviews by phone with 34 people who use drugs in Oregon from May to June 2021. We used thematic analysis to analyze transcripts and construct themes.

RESULTS

People who use drugs knew about fentanyl, expressed doubt that fentanyl could be found in methamphetamine; believed those who were younger or less experienced were at higher risk for harm; and received information about fentanyl from drug dealers, syringe service programs, or peers (other people who use drugs). Preference for fentanyl's presence in drugs like heroin or methamphetamine was mixed. Some felt that their preference was irrelevant since fentanyl was unavoidable. Participants reported engaging in harm reduction practices, including communicating about fentanyl with dealers and peers, testing for fentanyl, using smaller quantities of drugs, switching from injecting to smoking, and using naloxone.

CONCLUSION

People who use drugs are responding to the rise of fentanyl on the West Coast and are concerned about the increasing uncertainty and hazards of the drug supply. They are willing and motivated to adopt harm reduction behaviors. Harm reduction promotion from syringe service programs and public health agencies is essential to reduce injury and death from nonpharmaceutical fentanyl.

An overview of buprenorphine prescribing for the advanced practice psychiatric nurse

PURPOSE

Rates of at-risk opioid use, opioid use disorder, and opioid overdose remain alarmingly high. There are medications that can be used to treat opioid use disorder, including methadone, buprenorphine, and naltrexone, although access to care remains difficult. This review seeks to provide advanced practice psychiatric nurses (APPNs) with an overview of buprenorphine prescribing, with an emphasis on novel, long-acting delivery systems.

CONCLUSIONS

APPNs should be familiar with best practices regarding buprenorphine prescribing. Some patients may benefit from long-acting delivery methods, such as subdermal implants, or subcutaneous injections.

PRACTICE IMPLICATIONS

APPNs can reduce barriers to buprenorphine access and should be familiar with best practices related to buprenorphine prescribing.

Pharmacotherapy of Opioid Use Disorder-Update and Current Challenges

The incidence of opioid use disorder (OUD) and overdose deaths is rising yearly within the United States. Many cases are associated with illicitly manufactured fentanyl use. In addition to offering patients medications for OUD (methadone, buprenorphine, and naltrexone), the approach to this epidemic should involve increasing provider awareness and education about substance use disorders, expanding urine toxicology screens to test for fentanyl, and using low-threshold treatment approaches.

Sex-specific role of the circadian transcription factor NPAS2 in opioid tolerance, withdrawal and analgesia

Opioids like fentanyl remain the mainstay treatment for chronic pain. Unfortunately, opioid's high dependence liability has led to the current opioid crisis, in part, because of side-effects that develop during long-term use, including analgesic tolerance and physical dependence. Both tolerance and dependence to opioids may lead to escalation of required doses to achieve previous therapeutic efficacy. Additionally, altered sleep and circadian rhythms are common in people on opioid therapy. Opioids impact sleep and circadian rhythms, while disruptions to sleep and circadian rhythms likely mediate the effects of opioids. However, the mechanisms underlying these bidirectional relationships between circadian rhythms and opioids remain largely unknown. The circadian protein, neuronal PAS domain protein 2 (NPAS2), regulates circadian-dependent gene transcription in structure of the central nervous system that modulate opioids and pain. Here, male and female wild-type and NPAS2-deficient (NPAS2-/-) mice were used to investigate the role of NPAS2 in fentanyl analgesia, tolerance, hyperalgesia and physical dependence. Overall, thermal pain thresholds, acute analgesia and tolerance to a fixed dose of fentanyl were largely similar between wild-type and NPAS2-/- mice. However, female NPAS2-/- exhibited augmented analgesic tolerance and significantly more behavioral symptoms of physical dependence to fentanyl. Only male NPAS2-/- mice had increased fentanyl-induced hypersensitivity, when compared with wild-type males. Together, our findings suggest sex-specific effects of NPAS2 signaling in the regulation of fentanyl-induced tolerance, hyperalgesia and dependence.

Trace residue identification, characterization, and longitudinal monitoring of the novel synthetic opioid β-U10, from discarded drug paraphernalia

Empirical data regarding dynamic alterations in illicit drug supply markets in response to the COVID-19 pandemic, including the potential for introduction of novel drug substances and/or increased poly-drug combination use at the "street" level, that is, directly proximal to the point of consumption, are currently lacking. Here, a high-throughput strategy employing ambient ionization-mass spectrometry is described for the trace residue identification, characterization, and longitudinal monitoring of illicit drug substances found within >6,600 discarded drug paraphernalia (DDP) samples collected during a pilot study of an early warning system for illicit drug use in Melbourne, Australia from August 2020 to February 2021, while significant COVID-19 lockdown conditions were imposed. The utility of this approach is demonstrated for the de novo identification and structural characterization of β-U10, a previously unreported naphthamide analog within the "U-series" of synthetic opioid drugs, including differentiation from its α-U10 isomer without need for sample preparation or chromatographic separation prior to analysis. Notably, β-U10 was observed with 23 other drug substances, most commonly in temporally distinct clusters with heroin, etizolam, and diphenhydramine, and in a total of 182 different poly-drug combinations. Longitudinal monitoring of the number and weekly "average signal intensity" (ASI) values of identified substances, developed here as a semi-quantitative proxy indicator of changes in availability, relative purity and compositions of street level drug samples, revealed that increases in the number of identifications and ASI for β-U10 and etizolam coincided with a 50% decrease in the number of positive detections and an order of magnitude decrease in the ASI for heroin.

Preventing nausea and vomiting after gynecological laparoscopic surgery by patient-controlled intravenous analgesia with a naloxone admixture: A randomized controlled trial

BACKGROUND

Opioid-induced nausea and vomiting are common side effects of patient-controlled intravenous analgesia (PCIA). This study aimed to explore the inhibitory effect of a naloxone admixture on the incidence of sufentanil-induced postoperative nausea and vomiting (PONV).

METHODS

A total of 132 Uyghur American Society of Anesthesiologists I and II patients scheduled to undergo elective gynecological laparoscopic surgery were recruited; among these, 120 patients were enrolled and randomly allocated into 4 groups: patients receiving PCIA but no naloxone were included in the control group (group A); patients receiving PCIA with a low-dose naloxone admixture at 0.2 μg·kg-1·h-1 were included in group B; patients receiving PCIA with naloxone admixture at 0.4 μg·kg-1·h-1 were included in group C; patients receiving PCIA with naloxone admixture at 0.6 μg·kg-1·h-1 were included in group D. All patients were administered sufentanil at 0.04 kg-1·h-1, butorphanol at 2 kg-1·h-1, and dexmedetomidine at 0.08 kg-1·h-1 using a PCIA device within 2 days of surgery. The occurrence of nausea and vomiting, visual analogue scores for pain intensity, mean arterial pressure, heart rate, oxygen saturation, pruritus, lethargy, respiratory depression, etc, was recorded at 2, 8, 12, 24, and 48 hours postoperatively.

RESULTS

There was a significant difference in the PONV scores between the groups at 8, 12, and 24 hours after surgery (P < 0.01). At 8 and 12 hours, the score of group C/D was significantly lower than that of group A/B (P < 0.01). At 24 hours after surgery, the PONV score of group B/C/D was significantly lower than that of group A (P < 0.01). No significant difference was observed in the general data and visual analogue scores for postoperative pain between the 4 groups.

CONCLUSION

Naloxone admixture administered at 0.4 to 0.6 μg·kg-1·h-1 can exert an effective inhibitory effect on the incidence and intensity of PONV in gynecological laparoscopic surgery.

Reports of Adverse Events Associated with Use of Novel Psychoactive Substances, 2017-2020: A Review

An important role of modern forensic and clinical toxicologists is to monitor the adverse events of novel psychoactive substances (NPS). Following a prior review from 2013 to 2016, this critical literature review analyzes and evaluates published case reports for NPS from January 2017 through December 2020. The primary objective of this study is to assist in the assessment and interpretation of these cases as well as provide references for confirmation methods. Chemistry, pharmacology, adverse events and user profiles (e.g., polypharmacy) for NPS are provided including case history, clinical symptoms, autopsy findings and analytical results. Literature reviews were performed in PubMed and Google Scholar for publications using search terms such as NPS specific names, general terms (e.g., 'designer drugs' and 'novel psychoactive substances'), drug classes (e.g., 'designer stimulants') and outcome-based terms (e.g., 'overdose' and 'death'). Government and website drug surveillance databases and abstracts published by professional forensic science organizations were also searched. Toxicological data and detailed case information were extracted, tabulated, analyzed and organized by drug category. Case reports included overdose fatalities (378 cases), clinical treatment and hospitalization (771 cases) and driving under the influence of drugs (170 cases) for a total of 1,319 cases providing details of adverse events associated with NPS. Confirmed adverse events with associated toxidromes of more than 60 NPS were reported including synthetic cannabinoid, NPS stimulant, NPS hallucinogen, NPS benzodiazepine and NPS opioid cases. Fifty of these NPS were reported for the first time in January 2017 through December 2020 as compared to the previous 4 years surveyed. This study provides insight and context of case findings described in the literature and in digital government surveillance databases and websites during a recent 4-year period. This review will increase the awareness of adverse events associated with NPS use to better characterize international emerging drug threats.

Pharmacological affinity fingerprints derived from bioactivity data for the identification of designer drugs

Facing the continuous emergence of new psychoactive substances (NPS) and their threat to public health, more effective methods for NPS prediction and identification are critical. In this study, the pharmacological affinity fingerprints (Ph-fp) of NPS compounds were predicted by Random Forest classification models using bioactivity data from the ChEMBL database. The binary Ph-fp is the vector consisting of a compound's activity against a list of molecular targets reported to be responsible for the pharmacological effects of NPS. Their performance in similarity searching and unsupervised clustering was assessed and compared to 2D structure fingerprints Morgan and MACCS (1024-bits ECFP4 and 166-bits SMARTS-based MACCS implementation of RDKit). The performance in retrieving compounds according to their pharmacological categorizations is influenced by the predicted active assay counts in Ph-fp and the choice of similarity metric. Overall, the comparative unsupervised clustering analysis suggests the use of a classification model with Morgan fingerprints as input for the construction of Ph-fp. This combination gives satisfactory clustering performance based on external and internal clustering validation indices.

S-Nitroso-L-Cysteine Stereoselectively Blunts the Deleterious Effects of Fentanyl on Breathing While Augmenting Antinociception in Freely-Moving Rats

Endogenous and exogenously administered S-nitrosothiols modulate the activities of central and peripheral systems that control breathing. We have unpublished data showing that the deleterious effects of morphine on arterial blood-gas chemistry (i.e., pH, pCO2, pO2, and sO2) and Alveolar-arterial gradient (i.e., index of gas exchange) were markedly diminished in anesthetized Sprague Dawley rats that received a continuous intravenous infusion of the endogenous S-nitrosothiol, S-nitroso-L-cysteine. The present study extends these findings by showing that unanesthetized adult male Sprague Dawley rats receiving an intravenous infusion of S-nitroso-L-cysteine (100 or 200 nmol/kg/min) markedly diminished the ability of intravenous injections of the potent synthetic opioid, fentanyl (10, 25, and 50 μg/kg), to depress the frequency of breathing, tidal volume, and minute ventilation. Our study also found that the ability of intravenously injected fentanyl (10, 25, and 50 μg/kg) to disturb eupneic breathing, which was measured as a marked increase of the non-eupneic breathing index, was substantially reduced in unanesthetized rats receiving intravenous infusions of S-nitroso-L-cysteine (100 or 200 nmol/kg/min). In contrast, the deleterious effects of fentanyl (10, 25, and 50 μg/kg) on frequency of breathing, tidal volume, minute ventilation and non-eupneic breathing index were fully expressed in rats receiving continuous infusions (200 nmol/kg/min) of the parent amino acid, L-cysteine, or the D-isomer, namely, S-nitroso-D-cysteine. In addition, the antinociceptive actions of the above doses of fentanyl as monitored by the tail-flick latency assay, were enhanced by S-nitroso-L-cysteine, but not L-cysteine or S-nitroso-D-cysteine. Taken together, these findings add to existing knowledge that S-nitroso-L-cysteine stereoselectively modulates the detrimental effects of opioids on breathing, and opens the door for mechanistic studies designed to establish whether the pharmacological actions of S-nitroso-L-cysteine involve signaling processes that include 1) the activation of plasma membrane ion channels and receptors, 2) selective intracellular entry of S-nitroso-L-cysteine, and/or 3) S-nitrosylation events. Whether alterations in the bioavailability and bioactivity of endogenous S-nitroso-L-cysteine is a key factor in determining the potency/efficacy of fentanyl on breathing is an intriguing question.

Preclinical Efficacy and Selectivity of Vaccines Targeting Fentanyl, Alfentanil, Sufentanil, and Acetylfentanyl in Rats

The ongoing public health emergency of opioid use disorders (OUD) and overdose in the United States is largely driven by fentanyl and its related analogues and has resulted in over 75 673 deaths in 2021. Immunotherapeutics such as vaccines have been investigated as a potential interventional strategy complementary to current pharmacotherapies to reduce the incidence of OUD and opioid-related overdose. Given the importance of targeting structurally distinct fentanyl analogues, this study compared a previously established lead conjugate vaccine (F₁-CRM) to a series of novel vaccines incorporating haptens derived from alfentanil and acetylfentanyl (F_{8, 9a, 9b, 10}), and evaluated their efficacy against drug-induced pharmacological effects in rats. While no vaccine tested provided significant protection against alfentanil, lead formulations were effective in reducing antinociception, respiratory depression, and bradycardia elicited by fentanyl, sufentanil, and acetylfentanyl. Compared with control, vaccination with F₁-CRM also reduced drug levels in the brain of rats challenged with lethal doses of fentanyl. These data further support investigation of F₁-CRM as a candidate vaccine against fentanyl and selected analogues.

Efficacy and Selectivity of Monovalent and Bivalent Vaccination Strategies to Protect against Exposure to Carfentanil, Fentanyl, and Their Mixtures in Rats

Drug-related fatal overdoses have significantly increased in the past decade due to the widespread availability of illicit fentanyl and other potent synthetic opioids such as carfentanil. Deliberate or accidental consumption or exposure to carfentanil, fentanyl, and their mixture induces respiratory depression and bradycardia that can be difficult to reverse with the opioid receptor antagonist naloxone. Vaccines offer a promising strategy to reduce the incidence of fatalities associated with fentanyl-related substances, as well as treatment for opioid use disorder (OUD). This study reports monovalent and bivalent vaccination strategies that elicit polyclonal antibody responses effective in protecting against the pharmacological actions of carfentanil, fentanyl, or carfentanil/fentanyl mixtures. Rats were prophylactically immunized with individual conjugate vaccines containing either carfentanil- or fentanyl-based haptens, or their combination in bivalent vaccine formulations, and then challenged with carfentanil, fentanyl, or their mixture. First, these studies identified a lead vaccine protective against carfentanil-induced antinociception, respiratory depression, and bradycardia. Then, efficacy against both carfentanil and fentanyl was achieved through bivalent vaccination strategies that combined lead anti-carfentanil and anti-fentanyl vaccines via either heterologous prime/boost or co-administration immunization regimens. These preclinical data support the development of vaccines as a viable strategy to prevent toxicity from exposure to excessive doses of carfentanil, fentanyl, or their mixtures.

Peripheral Nerve Blocks Outperform General Anesthesia for Pain Control in Arthroscopic Rotator Cuff Repair: A Systematic Review and Meta-analysis

PURPOSE

The purpose of this review is to compare the effectiveness of different peripheral nerve blocks and general anesthesia (GA) in controlling postoperative pain after arthroscopic rotator cuff repair (ARCR).

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review was conducted for the period of January 1, 2005, to February 16, 2021, by searching the following databases: PubMed, Cochrane, Embase, and Arthroscopyjournal.org. The primary outcomes of interest included 1-hour, 24-hour, and 48-hour pain scores on a numeric rating scale or visual analog scale (VAS). Inclusion criteria were English language studies reporting on adults (≥18 years) undergoing ARCR with peripheral nerve blockade. To synthesize subjective pain score data at each evaluation time point across studies, we performed random-effects network meta-regression analyses accounting for baseline pain score as a covariate.

RESULTS

A total of 14 randomized controlled trials with 851 patients were included in the meta-analysis. Data from six different nerve block interventions, single-shot interscalene brachial plexus nerve block (s-ISB; 37.8% [322/851]), single-shot suprascapular nerve block (s-SSNB; 9.9% [84/851]), continuous ISB (c-ISB; 17.5% [149/851]), continuous SSNB (c-SSNB; 6.9% [59/851]), s-ISB combined with SSNB (s-ISB+SSNB; 5.8% [49/851]), s-SSNB combined with axillary nerve block (s-SSNB+ANB; 4.8% [41/851]), as well as GA (17.3% [147/851]) were included. Our meta-analysis demonstrated that c-ISB block had a significant reduction in pain score relative to GA at 1-hour postoperation (mean difference [MD]: -1.8; 95% credible interval [CrI] = -3.4, -.08). There were no significant differences in VAS pain scores relative to GA at 24 and 48 hours postoperatively. However, s-ISB+SSNB had a significant reduction in 48-hour pain score compared to s-ISB (MD = -1.07; 95% CrI = -1.92, -.22).

CONCLUSIONS

It remains unclear which peripheral nerve block strategy is optimal for ARCR. However, peripheral nerve blocks are highly effective at attenuating postoperative ARCR pain and should be more widely considered as an alternative over general anesthesia alone.

LEVEL OF EVIDENCE

Level II Systematic review and meta-analysis of Level I and II studies.

An Update on the Implications of New Psychoactive Substances in Public Health

The emergence of new psychoactive substances has earned a great deal of attention, and several reports of acute poisoning and deaths have been issued involving, for instance, synthetic opiates. In recent years, there have been profound alterations in the legislation concerning consumption, marketing, and synthesis of these compounds; rapid alert systems have also been subject to changes, and new substances and new markets, mainly through the internet, have appeared. Their effects and how they originate in consumers are still mostly unknown, primarily in what concerns chronic toxicity. This review intends to provide a detailed description of these substances from the point of view of consumption, toxicokinetics, and health consequences, including case reports on intoxications in order to help researchers and public health agents working daily in this area.

Transdermal Polymeric Microneedle Sensing Platform for Fentanyl Detection in Biofluid

Opioid drugs are extremely potent synthetic analytes, and their abuse is common around the world. Hence, a rapid and point-of-need device is necessary to assess the presence of this compound in body fluid so that a timely countermeasure can be provided to the exposed individuals. Herein, we present an attractive microneedle sensing platform for the detection of the opioid drug fentanyl in real serum samples using an electrochemical detection method. The device contained an array of pyramidal microneedle structures that were integrated with platinum (Pt) and silver (Ag) wires, each with a microcavity opening. The working sensor was modified by graphene ink and subsequently with 4 (3-Butyl-1-imidazolio)-1-butanesulfonate) ionic liquid. The microneedle sensor showed direct oxidation of fentanyl in liquid samples with a detection limit of 27.8 μM by employing a highly sensitive square-wave voltammetry technique. The resulting microneedle-based sensing platform displayed an interference-free fentanyl detection in diluted serum without conceding its sensitivity, stability, and response time. The obtained results revealed that the microneedle sensor holds considerable promise for point-of-need fentanyl detection and opens additional opportunities for detecting substances of abuse in emergencies.

Associations of Fentanyl, Sufentanil, and Remifentanil With Length of Stay and Mortality Among Mechanically Ventilated Patients: A Registry-Based Cohort Study

Background: As the first-line treatment for mechanically ventilated patients with critical illness, fentanyl and its analogs (e.g., sufentanil and remifentanil) are commonly used in the intensive care unit (ICU). However, the pharmacokinetics, metabolism, and potency of these agents differed. Their effects on clinical outcomes have not been well-understood.

Materials and Methods: Using a well-established registry, we conducted a cohort study. Patients who consistently underwent mechanical ventilation (MV) for more than 24 h were identified. We used a time-varying exposure definition, in which we coded each type of opioids as prescribed or not prescribed on each day from initiation of MV to extubation and ICU discharge. We used Fine-Gray competing risk models to compare the effects of fentanyl, sufentanil, and remifentanil on hazards for extubation, ventilator mortality, ICU discharge, and ICU mortality. All models were adjusted using a combination of fixed-time and time-varying covariates. Missing data were imputed using multiple imputation by chained equations.

Results: A total of 8,165 patients were included. There were, respectively, 4,778, 4,008, and 2,233 patients receiving at least 1 day of fentanyl, sufentanil, and remifentanil dose. Compared to fentanyl, sufentanil was associated with shorter duration to extubation (hazard ratio 1.31, 95% CI, 1.20–1.41) and ICU discharge (hazard ratio 1.63, 95% CI, 1.38–1.92), and remifentanil was associated with shorter duration to extubation (hazard ratio 1.60, 95% CI, 1.40–1.84) and ICU discharge (hazard ratio 2.02, 95% CI, 1.43–2.84). No significant differences in time to extubation (Hazard ratio 1.14, 95% CI, 0.92–1.41) and ICU discharge (Hazard ratio 1.31, 95% CI, 0.81–2.14) were found between sufentanil and remifentanil. No differences were observed between any two of the agents regarding ventilator mortality or ICU mortality. The effects were similar in patients with versus without surgery.

Conclusion: Sufentanil and remifentanil may be superior to fentanyl in shortening the time to extubation and ICU discharge. The effects on ventilator mortality and ICU mortality appeared similar across these agents, while further research is warranted.

Pharmacokinetic considerations for community-based dosing of nasal naloxone in opioid overdose in adults

INTRODUCTION

The administration of the opioid antagonist naloxone in the community is a measure to prevent death from opioid overdose. Approved nasal naloxone sprays deliver initial doses of 0.9 to 8 mg. The level of the initial community dose is controversial, as the scientific base is weak.In this review knowledge of the pharmacokinetics of nasal, both approved and improvised nasal sprays, and intramuscular naloxone will be utilized to evaluate dose-effect relationships in previous studies of opioid overdose outcomes.

AREAS COVERED

The aim was to present scientifically based considerations on the initial nasal naloxone doses currently available, which reasonably balances the effect and adverse outcomes, given that at least two doses are at hand. Also included in these considerations is the challenge by illicitly manufactured fentanyl and analogs.This paper is based on both peer-reviewed and grey literature identified by several searches, of such as naloxone pharmacokinetics/formulations/outcomes/emergency medical services, in PubMed and Embase.

EXPERT OPINION

There is little scientific evidence that supports the use of initial systemic dosing that exceeds 0.8 mg in the community. Higher doses increase the risk of withdrawal symptoms feared in people who use opioids. Many obstacles may reduce the potential of community-administered naloxone.

The Evolving Regulatory Landscape for Fentanyl: China, India, and Global Drug Governance

The rise of the synthetic opioid epidemic has time and time again brought criticism on China and India, the world's two main producers of fentanyl and its chemical precursors. In the past few years, the two countries have attempted to strengthen regulations over fentanyl production and distribution, though its effects on global drug governance remain under scrutiny. This study used qualitative and comparative methods to investigate the current regulatory landscape for fentanyl, including its efficiency and potential loopholes in China and India. It concludes that although both China and India are actively and significantly attempting to step away from the global fentanyl supply chain, these efforts remain ineffective due to institutional loopholes, namely inadequate legislation and fragmented regulatory structures. From insights gained on global drug governance, we recommend a binding international convention concentrated on controlling fentanyl and its related substances, with further bilateral and multilateral cooperation among states as necessary complementation.

The metabolism of valerylfentanyl using human liver microsomes and zebrafish larvae

Valerylfentanyl, a novel synthetic opioid less potent than fentanyl, has been reported in biological samples, but there are limited studies on its pharmacokinetic properties. The goal of this study was to elucidate the metabolism of valerylfentanyl using an in vitro human liver microsome (HLM) model compared with an in vivo zebrafish model. Nineteen metabolites were detected with N-dealkylation-valeryl norfentanyl and hydroxylation as the major metabolic pathways. The major metabolites in HLMs were also detected in 30 day postfertilization zebrafish. An authentic liver specimen that tested positive for valerylfentanyl, among other opioids and stimulants, revealed the presence of a metabolite that shared transitions and retention time as the hydroxylated metabolite of valerylfentanyl but could not be confirmed without an authentic standard. 4-Anilino-N-phenethylpiperidine (4-ANPP), a common metabolite to other fentanyl analogs, was also detected. In this study, we elucidated the metabolic pathway of valerylfentanyl, confirmed two metabolites using standards, and demonstrated that the zebrafish model produced similar metabolites to the HLM model for opioids.

Opioid use disorder and the brain: a clinical perspective

Opioid use disorder (OUD) has gained increasing publicity and interest during recent years, with many countries describing problems of epidemic proportions with regard to opioid use and deaths related to opioids. While opioids are not themselves acutely neurotoxic, the chronic relapsing and remitting nature of this disorder means that individuals are often exposed to exogenous opioids for lengthy periods of time (either illicit or prescribed as treatment). We are increasingly characterizing the effect of such long-term opioid exposure on the brain. This narrative review aims to summarize the literature regarding OUD and the brain from a clinical perspective. Alterations of brain structure and function are discussed, as well as neurological and psychiatric disorders in OUD. Finally, we review current and new directions for assessment and treatment.

Emerging trends in point-of-care sensors for illicit drugs analysis

Consumption of illicit narcotic drugs and fatal or criminal activities under their influence has become an utmost concern worldwide. These drugs influence an individual's feelings, perceptions, and emotions by altering the state of consciousness and thus can result in serious safety breaches at critical workplaces. Point-of-care drug-testing devices have become the need-of-the-hour for many sections such as the law enforcement agencies, the workplaces, etc. for safety and security. This review focuses on the recent progress on various electrochemical and optical nanosensors developed for the analysis of the most common illicit drugs (or their metabolites) such as tetrahydrocannabinol (THC), cocaine (COC), opioids (OPs), amphetamines & methamphetamine, and benzodiazepine (BZDs). The paper also highlights the sensitivity and selectivity of various sensing modalities along with evolving parameters such as real-time monitoring and measurement via a smart user interface. An overall outlook of recent technological advances in point of care (POC) devices and guided insights and directions for future research is presented.

Invited Commentary: Drug Checking for Novel Insights Into the Unregulated Drug Supply

Tobias et al. (Am J Epidemiol. 2022;191 (2):241-247) present a novel analysis of time trends in fentanyl concentrations in the unregulated drug supply in British Columbia, Canada. The preexisting knowledge about unregulated drugs had come from law-enforcement seizures and postmortem toxicology. As both of these data sources are subject to selection bias, large-scale drug-checking programs are poised to be a crucial component of the public health response to the unrelenting increase in overdose in North America. As programs expand, we offer 2 guiding principles. First, the primary purpose of these programs is to deliver timely results to people who use drugs to mitigate health risks. Second, innovation is needed to go beyond criminal justice paradigms in laboratory analysis for a more nuanced understanding of health concerns. We provide examples of the role adulterants play in our understanding of drug harms. We also describe the applications and limitations of common laboratory assays, with implications for epidemiologic surveillance. While the research and direct service teams in British Columbia have taken groundbreaking steps, there is still a need to establish best practices for communicating results to sample donors in an approachable yet nonalarmist tone.

Electroanalysis of Fentanyl and Its New Analogs: A Review

The review describes fentanyl and its analogs as new synthetic opioids and the possibilities of their identification and determination using electrochemical methods (e.g., voltammetry, potentiometry, electrochemiluminescence) and electrochemical methods combined with various separation methods. The review also covers the analysis of new synthetic opioids, their parent compounds, and corresponding metabolites in body fluids, such as urine, blood, serum, and plasma, necessary for a fast and accurate diagnosis of intoxication. Identifying and quantifying these addictive and illicit substances and their metabolites is necessary for clinical, toxicological, and forensic purposes. As a reaction to the growing number of new synthetic opioid intoxications and increasing fatalities observed over the past ten years, we provide thorough background for developing new biosensors, screen-printed electrodes, or other point-of-care devices.

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.

Thermal desorption bridged the gap between dielectric barrier discharge ionization and dried plasma spot samples for sensitive and rapid detection of fentanyl analogs in mass spectrometry

Guided by finite element simulations and 3D-printing, we constructed a semi-covered flat-TD surface for sufficient thermal desorption and ionization of fentanyl analogs from dried plasma/blood spot samples.

New Synthetic Opioids Use among Patients in Treatment for an Opioid Use Disorder in Barcelona

INTRODUCTION

New synthetic opioids (NSO), a class of new psychoactive substances (NPS), have recently emerged and pose an upcoming global public health challenge. The effects produced by NSO are similar to those from morphine, but they present greater pharmacological potency and abuse potential. Due to the increasing number of fatal overdoses and seizures in which NSO have been detected as heroin substitutes or adulterants, individuals with Opioid Use Disorder (OUD) represent a vulnerable population. The aim of our study was to describe and characterize from a gender perspective a Spanish cohort of potential conscious or unconscious NSO users.

METHODS

A cross-sectional study was conducted in a cohort of OUD participants under treatment in addiction care services in Barcelona and Badalona, Spain. Clinical evaluation was performed through an ad hoc survey, a scale to evaluate reasons to use an opioid without prescription (range 0-4) and the Wellbeing Index (WHO-5) (range 0-100). Objective consumption of NSO was assessed by urinalysis carried out by two validated methods: high-sensitivity gas chromatography-mass spectrometry (MS) and ultra-high-performance liquid chromatography-high-resolution MS.

RESULTS

A total of 154 participants with OUD were enrolled. They were mainly men (72.7%), mean age 47.8 years. Methadone was the predominant medication for opioid agonist treatment (mean dose 61.25 mg/day). A total of 32 (20.8%) participants reported having consumed some opioid to become "high" in the previous 3 months. The principal reasons for consuming illicit opioids were Replacing other drugs (mean 2.03) and Availability (mean 1.62), although Low price, was more highly valued by men (p = 0.045) and Shorter effect duration, most highly rated by women (p = <0.001). In the WHO-5, the mean score was 55 (SD = 30.1) without differences by gender. Fentanyl and derivatives or/and metabolites were detected in 7 (6.1%) participants, but illicit/non-prescribed NSOs were found in 5 out of 114 patients (4.4%), and other non-fentanyl opioids in 36 participants (26 men and 10 women).

CONCLUSION

A non-negligible consumption of NSO-fentanyl's (positive detection in 6.1% of biological samples) was detected. The reasons for using these substances and also the well-being differed between the genders. There is therefore both voluntary and involuntary NSO consumption in our country which highlights the importance of approaching this potential public health problem.

Kinetics and Mechanism of Fentanyl Dissociation from the μ-Opioid Receptor

Driven by illicit fentanyl, opioid related deaths have reached the highest level in 2020. Currently, an opioid overdose is resuscitated by the use of naloxone, which competitively binds and antagonizes the μ-opioid receptor (mOR). Thus, knowledge of the residence times of opioids at mOR and the unbinding mechanisms is valuable for assessing the effectiveness of naloxone. In the present study, we calculate the fentanyl-mOR dissociation time and elucidate the mechanism by applying an enhanced sampling molecular dynamics (MD) technique. Two sets of metadynamics simulations with different initial structures were performed while accounting for the protonation state of the conserved H297^6.52, which has been suggested to modulate the ligand-mOR affinity and binding mode. Surprisingly, with the Nδ-protonated H297^6.52, fentanyl can descend as much as 10 Å below the level of the conserved D147^3.32 before escaping the receptor and has a calculated residence time τ of 38 s. In contrast, with the Nϵ- and doubly protonated H297^6.52, the calculated τ are 2.6 and 0.9 s, respectively. Analysis suggests that formation of the piperidine-Hid297 hydrogen bond strengthens the hydrophobic contacts with the transmembrane helix (TM) 6, allowing fentanyl to explore a deep pocket. Considering the experimental τ of ∼4 min for fentanyl and the role of TM6 in mOR activation, the deep insertion mechanism may be biologically relevant. The work paves the way for large-scale computational predictions of opioid dissociation rates to inform evaluation of strategies for opioid overdose reversal. The profound role of the histidine protonation state found here may shift the paradigm in computational studies of ligand-receptor kinetics.

Pharmacokinetic Characterisation and Comparison of Bioavailability of Intranasal Fentanyl, Transmucosal, and Intravenous Administration through a Three-Way Crossover Study in 24 Healthy Volunteers

Background

For more than 60 years, the synthetic opioid fentanyl has been widely used in anaesthesia and analgesia. While the intravenous formulation is primarily used for general anaesthesia and intensive care settings, the drug's high lipophilic properties also allow various noninvasive routes of administration. Published data suggest that intranasal administration is also attractive for use as intranasal patient-controlled analgesia (PCA). A newly developed intranasal fentanyl formulation containing 47 μg fentanyl, intravenous fentanyl, and oral transmucosal fentanyl citrate were characterised, and bioavailability was compared to assess the suitability of the intranasal formulation for an intranasal PCA product.

Methods

27 healthy volunteers were enrolled in a single-centre, open-label, randomised (order of treatments), single-dose study in a three-period crossover design. The pharmacokinetics of one intranasal puff of fentanyl formulation (47 μg, 140 mL per puff), one short intravenous infusion of 50 μg fentanyl, and one lozenge with an integrated applicator (200 μg fentanyl) were studied, and bioavailability was calculated. Blood samples were collected over 12 hours, and plasma concentrations of fentanyl were determined by HPLC with MS/MS detection.

Results

24 volunteers completed the study. The geometric mean of AUC_0-tlast was the highest with oral transmucosal administration (1106 h ∗ pg/ml, CV% = 32.86), followed by intravenous (672 h ∗ pg/ml, CV% = 32.18) and intranasal administration (515 h ∗ pg/ml, CV% = 30.10). C _max was 886 pg/ml (CV% = 59.38) for intravenous, 338 pg/ml (CV% = 45.61) for intranasal, and 310 pg/ml (CV% = 29.58) for oral transmucosal administration. t _max was shortest for intravenous administration (0.06 h, SD = 0.056), followed by intranasal (0.21 h, SD = 0.078) and oral transmucosal administration (1.20 h, SD = 0.763). Dose-adjusted absolute bioavailability was determined to be 74.70% for the intranasal formulation and 41.25% for the oral transmucosal product. In total, 38 adverse events (AEs) occurred. Fourteen AEs were potentially related to the investigational items. No serious AE occurred.

Conclusion

Pharmacokinetic parameters and bioavailability of the investigated intranasal fentanyl indicated suitability for its intended use as an intranasal PCA option.

Risk of cardiovascular diseases in relation to substance use disorders

BACKGROUND

Substance use disorder (SUD) has become increasingly prevalent worldwide, this study investigated the associations of SUD and alcohol, cannabis, opioid, or stimulant use disorder with cardiovascular disease (CVD) and 11 major CVD subtypes.

METHODS

This study was based on a 20% random sample of residents in British Columbia, Canada, who were aged 18 - 80 years at baseline on January 1, 2015. Using linked administrative health data during 2010 - 2014, we identified people with various SUDs and prevalent CVDs at baseline, and examined the cross-sectional associations between SUDs and CVDs. After excluding people with CVDs at baseline, we followed the cohort for 4 years to identify people who developed incident CVDs, and examined the longitudinal associations between SUDs and CVDs.

RESULTS

The cross-sectional analysis at baseline included 778,771 people (mean age 45 years, 50% male), 13,279 (1.7%) had SUD, and 41,573 (5.3%) had prevalent CVD. After adjusting for covariates, people with SUD were 2.7 (95% confidence interval [CI], 2.5 - 2.8) times more likely than people without SUD to have prevalent CVD. The longitudinal analysis included 617,863 people, 17,360 (2.8%) developed incident CVD during the follow-up period. After adjusting for covariates, people with SUD were 1.7 (95% CI, 1.6 - 1.9) times more likely than people without SUD to develop incident CVD. The cross-sectional and longitudinal associations were more pronounced for people with opioid or stimulant use disorder.

CONCLUSIONS

People with SUD are more likely to have prevalent CVD and develop incident CVD compared with people without SUD.

The use of heat to deliver fentanyl via pulmonary drug delivery

The golden standard to treat acute pain is by intravenous drug delivery of opioids such as fentanyl or morphine. Intravenous drug delivery requires the placement of an intravenous (IV) port, which can cause infections, dislodgments, and distress to the patients, and therefore a non-invasive method is desirable. Pulmonary drug delivery is a non-invasive method that has been shown to be a good alternative to intravenous administration. New devices have been investigated for treating acute pain by delivering fentanyl by heat. The pure drug, fentanyl, is applied onto a surface which is then heated up to 350 °C and inhaled, resulting in no formation of degradation products. Furthermore, forced degradation of fentanyl has been studied which showed that longer heating time and higher temperatures will result in the formation of degradation products. The evidence indicates that heat can be used to deliver drugs to the lungs where fast onset reaction can be obtained giving fast and non-invasive pain relief.

Severe poisoning after smoking a mixture of 4-fluoroisobutyryl fentanyl (4-FiBF) and alpha-pyrolidinoisohexaphenone (α-PiHP)

CONTEXT

Intoxications after ingestion of new psychoactive substances are currently one of the most challenging issues in clinical toxicology. Synthetic cathinones represented the largest group of drugs seized in 2020, but the increasing distribution of fentanyl analogues is resulting in a growing global opioid crisis. In addition, synthetic opioids may be intentionally combined with psychostimulants by drug manufacturers to reduce depressive effects. We report a case of severe poisoning after smoking a mixture of 4-fluoroisobutyryl fentanyl (4-FiBF) and alpha-pyrrolidinoisohexaphenone (α-PiHP).

CASE DETAILS

A 29-year-old male was found out of conscious in his apartment and taken to the Intensive Care Unit. Examinations revealed pinpoint pupils, slight respiratory acidosis, leukocytosis as well as body temperature of 39.4 °C and increased creatinine with decreased eGFR level. Toxicological analysis of biological samples revealed presence of 4-FiBF and α-PiHP in concentrations: 87.7 ng/mL and 5.0 ng/mL (blood) and 2291.0 ng/mL and 722.2 ng/mL (urine), respectively. After 4 days, the patient was discharged home.

DISCUSSION

Unique combination of clinical symptoms was a result of a simultaneous 4-FiBF and α-PiHP intoxication. To our knowledge, this is the first case of ingestion such unusual mixture of new psychoactive substances with a full description of medical treatment.

Quantification of Classic, Prescription and Synthetic Opioids in Hair by LC-MS-MS

The current use and misuse of synthetic and prescription opioids in the USA has reached epidemic status. According to the US Department of Health and Human Services, every day more than 130 people in the USA die after overdosing on opioids, and 2.1 million had an opioid use disorder in 2018. Hair is becoming an alternative matrix of increasing interest in forensic toxicology to investigate drug use and abuse patterns due to its long window of detection. The focus of this project was to develop and validate a method that simultaneously detects and quantifies 27 classic, prescription and synthetic opioids in hair by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Hair samples were decontaminated and pulverized in a bead mill. Twenty-five milligrams of hair powder were incubated in a buffer overnight. Mixed mode cation exchange solid phase extraction was carried out before undergoing reversed-phase chromatographic separation, successfully resolving isobaric opioids. We used two multiple reaction monitoring transitions in positive mode to identify each analyte. The linearity range was 1-500 pg/mg for fentanyl and synthetic opioids and 10-500 pg/mg for prescription and classic opioids. Imprecision was <17.5% and bias ranged from -13.6 to 12.0%. Majority of compounds showed extraction efficiency >50%, and ion suppression from -89.2 to -26.6% (CV < 19%, n = 10). This method was applied to 64 authentic cases, identifying 13 compounds from our panel. A sensitive and specific method was developed for the identification and quantification of 27 classic, prescription and synthetic opioids in hair by LC-MS-MS.

Analysis of drug residue in needle-exchange syringes in Washington, D.C

For the first time in Washington, D.C., an analysis of drug residue from used needle-exchange syringes has been performed. This analysis is part of a larger initiative to understand the District of Columbia's illicit drug supply and its intravenous (IV) user's consumption trends as our nation faces the opioid epidemic. The goal of this study is to develop a more comprehensive monitoring program that provides real-time analysis necessary for public health organizations, in addition to providing initial observations of drugs detected. A total of 1187 syringes were analyzed over a period of nine months. Of these, 732 syringes (61.7%) were confirmed to contain a controlled dangerous substance (CDS). Fentanyl was detected in 490 syringes, the most observed CDS in all syringes analyzed. Heroin was the second most detected CDS, observed in 192 syringes. The third most detected CDS was cocaine, which was observed in 132 syringes, followed by the fourth most detected CDS, methamphetamine, observed in 82 syringes. Novel findings of this study include the first reported detections of methamphetamine, synthetic cathinones, and synthetic cannabinoids in used syringes in D.C. Ninety-seven syringes that contained no CDS contained a non-controlled substance of interest, such as diphenhydramine, xylazine, and etizolam. One limitation of this study is that this method cannot determine whether mixtures present in syringes stem from mixtures present prior to injection, back-to-back usage, or sharing of needles. This preliminary study illustrates the strength of surveillance to monitor drug trends and can be used to detect emerging novel dangerous substances in the future.

Improvements in Toxicology Testing to Identify Fentanyl Analogs and Other Novel Synthetic Opioids in Fatal Drug Overdoses, Connecticut, January 2016-June 2019

OBJECTIVES

Drug overdose deaths in Connecticut increasingly involve a growing number of fentanyl analogs and other novel nonfentanyl synthetic opioids (ie, novel synthetics). Current postmortem toxicology testing methods often lack the sophistication needed to detect these compounds. We examined how improved toxicology testing of fatal drug overdoses can determine the prevalence and rapidly evolving trends of novel synthetics.

METHODS

From 2016 to June 2019, the Connecticut Office of the Chief Medical Examiner increased its scope of toxicology testing of suspected drug overdose deaths in Connecticut from basic to enhanced toxicology testing to detect novel synthetics. The toxicology laboratory also expanded its testing panels during this time. We analyzed toxicology results to identify and quantify the involvement of novel synthetics over time.

RESULTS

From 2016 to June 2019, 3204 drug overdose deaths received enhanced toxicology testing; novel synthetics were detected in 174 (5.4%) instances. Ten different novel synthetics were detected with 205 total occurrences. Of 174 overdose deaths with a novel synthetic detected, most had 1 (n = 146, 83.9%) or 2 (n = 26, 14.9%) novel synthetics detected, with a maximum of 4 novel synthetics detected. Para-fluorobutyrylfentanyl/FIBF, furanylfentanyl, and U-47700 were most identified overall, but specific novel synthetics came in and out of prominence during the study period, and the variety of novel synthetics detected changed from year to year.

CONCLUSIONS

Enhanced toxicology testing for drug overdose deaths is effective in detecting novel synthetics that are not identified through basic toxicology testing. Identifying emerging novel synthetics allows for a timely and focused response to potential drug outbreaks and illustrates the changing drug market.

Development and evaluation of a synthetic opioid targeted gas chromatography mass spectrometry (GC-MS) method

As seized drug casework becomes increasingly complex due to the continued prevalence of emerging drugs, laboratories are often looking for new analytical approaches including developing methods for the analysis of specific compounds classes. Recent efforts have focused on the development of targeted gas chromatography mass spectrometry (GC-MS) confirmation methods to compliment the information-rich screening results produced by techniques like direct analysis in real time mass spectrometry (DART-MS). In this work, a method for the confirmation of synthetic opioids and related compounds was developed and evaluated. An 11-component test solution was used to develop a method that focused on minimizing overlapping retention time acceptance windows and understanding the influence of instrument parameters on reproducibility and sensitivity. Investigated settings included column type, flow rate, temperature program, inlet temperature, source temperature, and tune type. Using a DB-200 column, a 35-min temperature ramped method was created. It was evaluated against a suite of 222 synthetic opioids and related compounds, and successfully differentiated all but four compound pairs based on nonoverlapping retention time acceptance windows or objectively different mass spectra. Compared to a general confirmatory method used in casework, the targeted method was up to 25 times more sensitive and provided at least a two-fold increase in retention time differences. Analysis of extracts from actual case samples successfully demonstrated utility of the method and showed no instance of carryover, although the high polarity column required wider retention time windows than other columns.