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Evidence-based practices for reducing opioid-related overdose deaths include overdose education and naloxone distribution, the use of medications for the treatment of opioid use disorder, and prescription opioid safety. Data are needed on the effectiveness of a community-engaged intervention to reduce opioid-related overdose deaths through enhanced uptake of these practices. In this community-level, cluster-randomized trial, we randomly assigned 67 communities in Kentucky, Massachusetts, New York, and Ohio to receive the intervention (34 communities) or a wait-list control (33 communities), stratified according to state. The trial was conducted within the context of both the coronavirus disease 2019 (Covid-19) pandemic and a national surge in the number of fentanyl-related overdose deaths. The trial groups were balanced within states according to urban or rural classification, previous overdose rate, and community population. The primary outcome was the number of opioid-related overdose deaths among community adults. During the comparison period from July 2021 through June 2022, the population-averaged rates of opioid-related overdose deaths were similar in the intervention group and the control group (47.2 deaths per 100,000 population vs. 51.7 per 100,000 population), for an adjusted rate ratio of 0.91 (95% confidence interval, 0.76 to 1.09; P = 0.30). The effect of the intervention on the rate of opioid-related overdose deaths did not differ appreciably according to state, urban or rural category, age, sex, or race or ethnic group. Intervention communities implemented 615 evidence-based practice strategies from the 806 strategies selected by communities (254 involving overdose education and naloxone distribution, 256 involving the use of medications for opioid use disorder, and 105 involving prescription opioid safety). Of these evidence-based practice strategies, only 235 (38%) had been initiated by the start of the comparison year. In this 12-month multimodal intervention trial involving community coalitions in the deployment of evidence-based practices to reduce opioid overdose deaths, death rates were similar in the intervention group and the control group in the context of the Covid-19 pandemic and the fentanyl-related overdose epidemic. (Funded by the National Institutes of Health; HCS ClinicalTrials.gov number, NCT04111939.).

Rationale Isobutyryl-carfentanyl is the most recently discovered fentanyl analogue with a chemical structure that is similar to that of carfentanyl. Its analogue, carfentanyl, is regarded as one of the most lethal drugs in the world, with a potency of 10,000 times that of morphine. Therefore, isobutyryl-carfentanyl may possess a comparably high potency and its harmful effects cannot be ignored. Objectives This study was designed to assess the analgesic effect of isobutyryl-carfentanyl and the potential risks associated with its misuse. Methods In this study, we assessed the acute toxicity of isobutyryl-carfentanyl by up-and-down-procedure, the analgesic efficacy by hot-plate test, the abuse potential by conditioned place preference (CPP), drug self-administration, and drug discrimination tests, and compared it with fentanyl and carfentanyl. Results The estimated median lethal dose (LD 50 ) of isobutyryl-carfentanyl administered were 175 mg/kg (intragastric administration, IG), 15.84 mg/kg (intraperitoneal injection, IP), 15.84 mg/kg (subcutaneous injection, SC), and 1.6 mg/kg (intravenous injection, IV), respectively. The 50% maximal analgesic effect (ED 50 ) of isobutyryl-carfentanyl was determined to be 0.00319 mg/kg, with an analgesic potency 14 times that of fentanyl and 0.82 times that of carfentanyl. Isobutyryl-carfentanyl exhibited a significant positional preference at a minimum dose of 0.1 mg/kg, while fentanyl exhibited a significant positional preference at a minimum dose of 0.3 mg/kg. In the heroin (0.05 mg/kg/infusion) self-administration substitution experiment, isobutyryl-carfentanyl showed significant self-administration behaviour at doses of 0.0005–0.001 mg/kg/infusion, with the maximum number of infusions observed at a dose of 0.001 mg/kg. In the heroin (1 mg/kg) drug discrimination experiment, fentanyl (0.005–0.02 mg/kg), carfentanyl (0.0005–0.002 mg/kg), and isobutyryl-carfentanyl (0.001–0.005 mg/kg) were tested in the dose-effect curves. The results showed that all three drugs exhibit dose-dependent increase in the number of drug-associated nose pokes responses and reduction in the rate of nose pokes. The subjective effect potency of isobutyryl-carfentanyl was found to be 4.4 times that of fentanyl and 0.5 times that of carfentanyl. Conclusions In summary, isobutyryl-carfentanyl has high acute toxicity and analgesic effect, with strong psychological dependence approximately 5 times that of fentanyl and 0.5 times that of carfentanyl, and has extremely high abuse potency.

•Acrylfentanyl caused 40 fatal intoxications in Sweden between April and October 2016.•Non-fatal acrylfentanyl intoxications occurred in lower number.•Acrylfentanyl and other new fentanyl-analogs keep appearing on the drug market. The European Nordic Countries are the most exposed to opioid-related deaths. Between April and October 2016, a series of forty lethal intoxications occurred in Sweden, in which the presence of the synthetic opioid acrylfentanyl was determined to be the main – or a contributing – cause of death. In the reported cases, the blood concentration of acrylfentanyl – mostly detected in combination with other drugs – ranged from 0.01ng/g to 5ng/g; victims were predominantly males (34 males and 6 females), and their age varied between 18 and 53 years. We further describe five cases, representative of the different drug administration route (nasal spray, tablets) and intentions (accidental or voluntary intoxication). Moreover, we address nine cases of non-lethal intoxication, in single (8 cases) or polydrug scenario (1 case). We discuss the present characteristics of the Swedish drug market for fentanyl-analogs in general and acrylfentanyl in particular, reporting a structural difficulty to effectively counteracting the appearance of unscheduled substances due to the constant turnover of new molecules on the recreational drug market.

Up to now, little is known about the metabolic pathways of new fentanyl analogs that have recently emerged on the drug markets worldwide with high potential for producing addiction and severe adverse effects including coma and death. For some of the compounds, limited information on the metabolism has been published, however, for others so far no information is available. Considering the well characterized metabolism of the pharmaceutically used opioid fentanyl and the so far available data, the metabolism of the new fentanyl analogs can be anticipated to generally involve reactions like hydrolysis, hydroxylation (and further oxidation steps), - and -dealkylation and -methylation. Furthermore, phase II metabolic reactions can be expected comprising glucuronide or sulfate conjugate formation. When analyzing blood and urine samples of acute intoxication cases or fatalities, the presence of metabolites can be crucial for confirmation of the uptake of such compounds and further interpretation. Here we present a review on the metabolic profiles of new fentanyl analogs responsible for a growing number of severe and fatal intoxications in the United States, Europe, Canada, Australia, and Japan in the last years, as assessed by a systematic search of the scientific literature and official reports.

RationaleThe potent synthetic opioid fentanyl, and its analogs, continue to drive opioid-related overdoses. Although the pharmacology of fentanyl is well characterized, there is little information about the reinforcing effects of clandestine fentanyl analogs (FAs).ObjectivesHere, we compared the effects of fentanyl and the FAs acetylfentanyl, butyrylfentanyl, and cyclopropylfentanyl on drug self-administration in male and female rats. These FAs feature chemical modifications at the carbonyl moiety of the fentanyl scaffold.MethodsSprague-Dawley rats fitted with intravenous jugular catheters were placed in chambers containing two nose poke holes. Active nose poke responses resulted in drug delivery (0.2 mL) over 2 s on a fixed-ratio 1 schedule, followed by a 20 s timeout. Acquisition doses were 0.01 mg/kg/inj for fentanyl and cyclopropylfentanyl, and 0.03 mg/kg/inj for acetylfentanyl and butyrylfentanyl. After 10 days of acquisition, dose-effect testing was carried out, followed by 10 days of saline extinction.ResultsSelf-administration of fentanyl and FAs was acquired by both male and female rats, with no sex differences in acquisition rate. Fentanyl and FAs showed partial inverted-U dose-effect functions; cyclopropylfentanyl and fentanyl had similar potency, while acetylfentanyl and butyrylfentanyl were less potent. Maximal response rates were similar across drugs, with fentanyl and cyclopropylfentanyl showing maximum responding at 0.001 mg/kg/inj, acetylfentanyl at 0.01 mg/kg/inj, and butyrylfentanyl at 0.003 mg/kg/inj. No sex differences were detected for drug potency, efficacy, or rates of extinction.ConclusionsOur work provides new evidence that FAs display significant abuse liability in male and female rats, which suggests the potential for compulsive use in humans.

Indiscriminate activation of opioid receptors provides pain relief but also severe central and intestinal side effects. We hypothesized that exploiting pathological (rather than physiological) conformation dynamics of opioid receptor-ligand interactions might yield ligands without adverse actions. By computer simulations at low pH, a hallmark of injured tissue, we designed an agonist that, because of its low acid dissociation constant, selectively activates peripheral μ-opioid receptors at the source of pain generation. Unlike the conventional opioid fentanyl, this agonist showed pH-sensitive binding, heterotrimeric guanine nucleotide–binding protein (G protein) subunit dissociation by fluorescence resonance energy transfer, and adenosine 3′,5′-monophosphate inhibition in vitro. It produced injury-restricted analgesia in rats with different types of inflammatory pain without exhibiting respiratory depression, sedation, constipation, or addiction potential.

Xylazine — Medical and Public Health ImperativesUse of xylazine, most often in combination with other drugs such as fentanyl, is a rapidly growing health threat. People being harmed by this drug deserve rapid, comprehensive, and high-quality care.

Fentanyl is a powerful painkiller that elicits euphoria and positive reinforcement 1 . Fentanyl also leads to dependence, defined by the aversive withdrawal syndrome, which fuels negative reinforcement 2 , 3 (that is, individuals retake the drug to avoid withdrawal). Positive and negative reinforcement maintain opioid consumption, which leads to addiction in one-fourth of users, the largest fraction for all addictive drugs 4 . Among the opioid receptors, µ-opioid receptors have a key role 5 , yet the induction loci of circuit adaptations that eventually lead to addiction remain unknown. Here we injected mice with fentanyl to acutely inhibit γ-aminobutyric acid-expressing neurons in the ventral tegmental area (VTA), causing disinhibition of dopamine neurons, which eventually increased dopamine in the nucleus accumbens. Knockdown of µ-opioid receptors in VTA abolished dopamine transients and positive reinforcement, but withdrawal remained unchanged. We identified neurons expressing µ-opioid receptors in the central amygdala (CeA) whose activity was enhanced during withdrawal. Knockdown of µ-opioid receptors in CeA eliminated aversive symptoms, suggesting that they mediate negative reinforcement. Thus, optogenetic stimulation caused place aversion, and mice readily learned to press a lever to pause optogenetic stimulation of CeA neurons that express µ-opioid receptors. Our study parses the neuronal populations that trigger positive and negative reinforcement in VTA and CeA, respectively. We lay out the circuit organization to develop interventions for reducing fentanyl addiction and facilitating rehabilitation. Experiments using fentanyl treatment of mice show that µ-opioid receptors mediate positive reinforcement in the ventral tegmental area and negative reinforcement in central amygdala, thereby identifying the circuits that lead to opioid addiction.

Opioids are one of the most important and effective drug classes in pain medicine with a key role in most medical fields. The increase of opioid prescription over time has led to higher numbers of prescription opioid misuse, abuse and opioid-related deaths in most developed OECD (Organisation for Economic Co-operation and Development) countries around the world. Whilst reliable data on the prevalence of opioid treatment is accessible for many countries, data on Germany specifically is still scarce. Considering Germany being the largest country in the European Union, the lack of evidence-based strategies from long-term studies is crucial. The aim of this work is to review and summarise relevant published literature on the prevalence of opioid prescription in Germany to adequately inform health policy strategies. A systematic review of the epidemiology of opioid prescription in Germany was conducted, searching PubMed and Web of Science. Eligibility criteria were defined prior to conducting the search. Literature concerning Germany, published in English and German was included and the search was replicated by three independent researchers. Two levels of screening were employed. Disagreement was resolved by face-to-face discussion, leading to a consensus judgement. Our electronic search yielded 735 articles. Reviewing titles and abstracts yielded 19 relevant articles. Three authors examined each article's full text more closely and determined that twelve papers should be included. Of the twelve identified studies-with publication dates ranging from 1985 to 2016-six were retrospective cross-sectional studies and six were retrospective repeated-measures cross-sectional studies. Sample sizes ranged from 92,842 to ≈ 11,000,000 participants. Data sources of included studies showed vast heterogeneity. The reviewed literature suggested an increase in the number of patients with opioid prescriptions and defined daily doses of opioids per recipient in Germany over time. The majority of opioid prescriptions was used for patients with non-cancer pain. Opioid use was more common in older people, women and in the north of Germany. Fentanyl was shown to be the most prescribed strong opioid in outpatient settings in Germany, despite not being the first-line choice for chronic pain conditions. All data published before 2000-but none of the more recent studies-suggested an insufficient treatment of pain using opioids. There were no signs for a current opioid epidemic in Germany. Despite some limitations of the review and the heterogeneity of studies, it can be stated that the number of opioid prescriptions overall as well as the number of people receiving opioid treatment have increased over time. Most prescriptions were found to be for strong opioids and patients with non-cancer pain. Even though patterns of opioid prescription follow trends observed in other developed countries, there are no signs of an opioid epidemic in Germany. Therefore, this review could currently not find a need for urgent health policy interventions regarding opioid prescription practices. However, critical gaps in the literature remain and more research is needed to make more reliable judgements.