Nalbuphine Potentiates Reversal of Fentanyl Overdose by Naloxone.

Developing an effective antidote for fentanyl-induced overdose to achieve timely reversal is an unmet public health need. Previously, we found that naloxone derivative NX90 with mild κ-opioid agonistic properties was three-fold more effective than the parent naloxone in reversing a fentanyl overdose in rats. To investigate whether κ-agonistic properties could indeed augment the robustness of overdose reversal, we evaluated a κ-agonist/µ-antagonist nalbuphine (NB) as well as its combinations with naloxone (NX) in a fentanyl overdose model in rodents. An administration of either NB or NX as single agents at 0.1 mg/kg doses produced a full recovery in 90 ± 9.9 min and 11.4 ± 2.7 min, respectively. A higher dose of NX at 0.2 mg/kg reversed an overdose within 4.8 ± 1.0 min. In contrast to that, the coadministration of NB and NX at 0.1 mg/kg each produced a synergistic effect, with overdose reversal in 3.4 ± 0.2 min. The coadministration of NX and NB at sub-therapeutic doses of 0.05 mg/kg each was also 1.2-fold more effective than NX at 0.2 mg/kg. We further found that co-administration of NB at different doses (0.025, 0.05, 0.1 mg/kg) and ratios (1:4 and 1:1) with NX had differential effects on overdose reversal, cardiorespiratory liabilities, and analgesia.

Fentanyl Overdose Causes Prolonged Cardiopulmonary Dysregulation in Male SKH1 Mice.

Fentanyl overdose is a survivable condition that commonly resolves without chronic overt changes in phenotype. While the acute physiological effects of fentanyl overdose, such as opioid-induced respiratory depression (OIRD) and Wooden Chest Syndrome, represent immediate risks of lethality, little is known about longer-term systemic or organ-level impacts for survivors. In this study, we investigated the effects of a single, bolus fentanyl overdose on components of the cardiopulmonary system up to one week post. SKH1 mice were administered subcutaneous fentanyl at the highest non-lethal dose (62 mg/kg), LD10 (110 mg/kg), or LD50 (135 mg/kg), before euthanasia at 40 min, 6 h, 24 h, or 7 d post-exposure. The cerebral cortex, heart, lungs, and plasma were assayed using an immune monitoring 48-plex panel. The results showed significantly dysregulated cytokine, chemokine, and growth factor concentrations compared to time-matched controls, principally in hearts, then lungs and plasma to a lesser extent, for the length of the study, with the cortex largely unaffected. Major significant analytes contributing to variance included eotaxin-1, IL-33, and betacellulin, which were generally downregulated across time. The results of this study suggest that cardiopulmonary toxicity may persist from a single fentanyl overdose and have wide implications for the endurance of the expanding population of survivors.

Law enforcement fentanyl seizures and overdose mortality in US counties, 2013-2020.

BACKGROUND: The spread of illicitly manufactured fentanyl is driving steep increases in US overdose deaths. Fentanyl seizures are correlated with state-level opioid-related mortality; however, more granular seizure surveillance information has the potential to better inform overdose prevention and harm reduction efforts. METHODS: Using data on fentanyl pill and powder seizures from High Intensity Drug Trafficking Areas (HIDTA), we tested associations between seizure prevalence and overdose mortality, from 2013 to 2020. The primary exposure-seizure burden-was constructed by identifying counties having high (above the median) prevalence of pill, powder, or combined pill/powder seizure burden per 100,000 population. Poisson models accounted for county demographic, law enforcement and time trends. RESULTS: During the timeframe, there were 13,842 fentanyl seizures in 606 US counties. In adjusted models, counties with a high burden of pill or powder fentanyl seizures, or both (combined pills/powder) exhibited higher total overdose mortality than non-high burden counties (pills adjusted prevalence ratio [aPR]: 1.10 [95 % confidence interval [CI]: 1.08, 1.12]; powder aPR 1.12 [CI: 1.11, 1.13]; combined pills/powder aPR: 1.27 [CI: 1.25, 1.29]). A similar pattern of associations with fentanyl seizure burden was noted for overdose deaths involving synthetic opioids (pills [aPR]: 0.99 [CI: 0.96, 1.02]; powder aPR 1.29 [CI: 1.27, 1.30]; combined pills/powder aPR 1.55 [CI: 1.52, 1.58]). CONCLUSIONS: Law enforcement data on fentanyl seizures predicts drug overdose mortality at the county-level. Integrating these data with more traditional epidemiologic surveillance approaches has the potential to inform community overdose response efforts.

Opioid-Based Haptens: Development of Immunotherapy.

Over the past decades, extensive preclinical research has been conducted to develop vaccinations to protect against substance use disorder caused by opioids, nicotine, cocaine, and designer drugs. Morphine or fentanyl derivatives are small molecules, and these compounds are not immunogenic, but when conjugated as haptens to a carrier protein will elicit the production of antibodies capable of reacting specifically with the unconjugated hapten or its parent compound. The position of the attachment in opioid haptens to the carrier protein will influence the specificity of the antiserum produced in immunized animals with the hapten-carrier conjugate. Immunoassays for the determination of opioid drugs are based on the ability of drugs to inhibit the reaction between drug-specific antibodies and the corresponding drug-carrier conjugate or the corresponding labelled hapten. Pharmacological studies of the hapten-carrier conjugates resulted in the development of vaccines for treating opioid use disorders (OUDs). Immunotherapy for opioid addiction includes the induction of anti-drug vaccines which are composed of a hapten, a carrier protein, and adjuvants. In this review we survey the design of opioid haptens, the development of the opioid radioimmunoassay, and the results of immunotherapy for OUDs.

Combining surface-enhanced Raman spectroscopy (SERS) and paper spray mass spectrometry (PS-MS) for illicit drug detection.

There is an ongoing effort in the US illicit drug market to make new psychoactive compounds more potent and addictive. Due to continuous chemical modifications, many fentanyl analogs are developed and mixed with more traditional illicit drugs, such as cocaine and heroin. Detecting fentanyl and fentanyl analogs in these illicit drug mixtures has become more crucial because of the increased potency and associated health risks. Most confirmatory procedures require time-consuming and expensive, highly sophisticated laboratory equipment and experimental procedures, which can delay critical information that might save a victim or find a suspect. In this study, we propose miniaturizing and accelerating this process by combining surface-enhanced Raman spectroscopy (SERS) analysis and paper spray mass spectrometry (PS-MS). For this aim, dual-purposed paper substrates were developed through soaking in Au/Ag nanostars suspensions. These novel, in-house prepared paper SERS substrates showed stability for up to four weeks with and without the presence of drug compounds. Fentanyl analogs with similar SERS spectra were differentiated by coupling with PS-MS. The limit of detection (LOD) for fentanyl on the paper substrates is 34 µg/mL and 0.32 µg/mL for SERS and PS-MS, respectively. Fentanyl and fentanyl analogs show selective SERS enhancement that helped to detect trace amounts of these opioids in heroin and cocaine street samples. In short, we propose the combination of SERS/PS-MS by using modified paper substrates to develop cost-effective, sensitive, rapid, portable, reliable, and reproducible methods to detect illicit drugs, especially trace amounts of fentanyl and fentanyl analogs in illicit drug mixtures. The combination of these two category A techniques allows for the identification of illicit drugs according to the SWGDRUG guidelines.

Comparison of intranasal naloxone and intranasal nalmefene in a translational model assessing the impact of synthetic opioid overdose on respiratory depression and cardiac arrest.

Introduction: Using a validated translational model that quantitatively predicts opioid-induced respiratory depression and cardiac arrest, we compared cardiac arrest events caused by synthetic opioids (fentanyl, carfentanil) following rescue by intranasal (IN) administration of the µ-opioid receptor antagonists naloxone and nalmefene. Methods: This translational model was originally developed by Mann et al. (Clin Pharmacol Ther 2022) to evaluate the effectiveness of intramuscular (IM) naloxone. We initially implemented this model using published codes, reproducing the effects reported by Mann et al. on the incidence of cardiac arrest events following intravenous doses of fentanyl and carfentanil as well as the reduction in cardiac arrest events following a standard 2 mg IM dose of naloxone. We then expanded the model in terms of pharmacokinetic and µ-opioid receptor binding parameters to simulate effects of 4 mg naloxone hydrochloride IN and 3 mg nalmefene hydrochloride IN, both FDA-approved for the treatment of opioid overdose. Model simulations were conducted to quantify the percentage of cardiac arrest in 2000 virtual patients in both the presence and absence of IN antagonist treatment. Results: Following simulated overdoses with both fentanyl and carfentanil in chronic opioid users, IN nalmefene produced a substantially greater reduction in the incidence of cardiac arrest compared to IN naloxone. For example, following a dose of fentanyl (1.63 mg) producing cardiac arrest in 52.1% (95% confidence interval, 47.3-56.8) of simulated patients, IN nalmefene reduced this rate to 2.2% (1.0-3.8) compared to 19.2% (15.5-23.3) for IN naloxone. Nalmefene also produced large and clinically meaningful reductions in the incidence of cardiac arrests in opioid naïve subjects. Across dosing scenarios, simultaneous administration of four doses of IN naloxone were needed to reduce the percentage of cardiac arrest events to levels that approached those produced by a single dose of IN nalmefene. Conclusion: Simulations using this validated translational model of opioid overdose demonstrate that a single dose of IN nalmefene produces clinically meaningful reductions in the incidence of cardiac arrest compared to IN naloxone following a synthetic opioid overdose. These findings are especially impactful in an era when >90% of all opioid overdose deaths are linked to synthetic opioids such as fentanyl.

Barriers to, and Facilitators of, Checking Drugs for Adulterants in the Era of Fentanyl and Xylazine: Qualitative Study.

BACKGROUND: Overdose deaths continue to reach new records in New York City and nationwide, largely driven by adulterants such as fentanyl and xylazine in the illicit drug supply. Unknowingly consuming adulterated substances dramatically increases risks of overdose and other health problems, especially when individuals consume multiple adulterants and are exposed to a combination of drugs they did not intend to take. Although test strips and more sophisticated devices enable people to check drugs for adulterants including fentanyl and xylazine prior to consumption and are often available free of charge, many people who use drugs decline to use them. OBJECTIVE: We sought to better understand why people in the New York City area do or do not check drugs before use. We plan to use study findings to inform the development of technology-based interventions to encourage consistent drug checking. METHODS: In summer 2023, team members who have experience working with people who use drugs conducted 22 semistructured qualitative interviews with a convenience sample of people who reported illicit drug use within the past 90 days. An interview guide examined participants' knowledge of and experience with adulterants including fentanyl, xylazine, and benzodiazepines; using drug testing strips; and whether they had ever received harm reduction services. All interviews were audio recorded, transcribed, and analyzed for emerging themes. RESULTS: Most participants lacked knowledge of adulterants, and only a few reported regularly checking drugs. Reasons for not checking included lacking convenient access to test supplies, or a place to check samples out of the public's view, as well as time considerations. Some participants also reported a strong belief that they were not at risk from fentanyl, xylazine, or other adulterants because they exclusively used cocaine or crack, or that they were confident the people they bought drugs from would not sell them adulterated substances. Those who did report testing their drugs described positive interactions with harm reduction agency staff. CONCLUSIONS: New forms of outreach are needed not only to increase people's knowledge of adulterated substances and awareness of the increasing risks they pose but also to encourage people who use drugs to regularly check their substances prior to use. This includes new intervention messages that highlight the importance of drug checking in the context of a rapidly changing and volatile drug supply. This messaging can potentially help normalize drug checking as an easily enacted behavior that benefits public health. To increase effectiveness, messages can be developed with, and outreach can be conducted by, trusted community members including people who use drugs and, potentially, people who sell drugs. Pairing this messaging with access to no-cost drug-checking supplies and equipment may help address the ongoing spiral of increased overdose deaths nationwide.

Alfentanil versus fentanyl for emergency department rapid sequence induction with ketamine: A-FAKT, a pilot randomized trial.

BACKGROUND: Fentanyl is often administered during rapid sequence induction of anesthesia (RSI) in the emergency department (ED) to ameliorate the hypertensive response that may occur. Due to its more rapid onset, the use of alfentanil may be more consistent with both the onset time of the sedative and the commencement of laryngoscopy. As such, we compared the effect of alfentanil and fentanyl on post-induction hemodynamic changes when administered as part of a standardized induction regimen including ketamine and rocuronium in ED RSI. METHODS: This was a double-blind pilot randomized controlled trial of adult patients requiring RSI in the ED of three urban Australian hospitals. Patients were randomized to receive either alfentanil or fentanyl in addition to ketamine and rocuronium for RSI. Non-invasive blood pressure and heart rate were measured immediately before and at two, four, and six minutes after induction. The primary outcome was the occurrence of at least one post-induction systolic blood pressure outside the pre-specified range of 100-160mmHg (with adjustment for patients with baseline hypertension). Secondary outcomes included hypertension, hypotension, hypoxia, first-pass intubation success, 30-day mortality, and the pattern of hemodynamic changes. RESULTS: A total of 61 patients were included in the final analysis (31 in the alfentanil group and 30 in the fentanyl group). The primary outcome was met in 58% of the alfentanil group and 50% of the fentanyl group (difference 8%, 95% confidence interval: -17% to 33%). The 30-day mortality rate, first-pass success rate, and incidences of hypertension, hypotension, and hypoxia were similar between the groups. There were no significant differences in systolic blood pressure or heart rate between the groups at any of the measured time-points. CONCLUSION: Alfentanil and fentanyl produced comparable post-induction hemodynamic changes when used as adjuncts to ketamine in ED RSI. Future studies could consider comparing different dosages of these opioids.

Fentanyl, carfentanil and other fentanyl analogues in Canada's illicit opioid supply: A cross-sectional study.

Background: Despite the increase in fentanyl-involved overdose deaths in Canada, there have been no national-level studies evaluating the proportion of illicit opioids containing fentanyl or fentanyl analogues in Canada. Methods: This cross-sectional exploratory study characterized trends in fentanyl, carfentanil and other fentanyl analogues within opioids seized by law enforcement agencies in Canada from 2012 to 2022 and submitted to the Health Canada Drug Analysis Service (DAS). Analyses were stratified by province/region. Mann-Kandell tests were used to test for trends. Results: A total of 157,616 samples containing any opioid ("opioid-containing samples") were submitted to the DAS from Canadian provinces between 2012 and 2022, of which 81,165 (51.5%) contained fentanyl or a fentanyl analogue. The percentage of opioid-containing samples that were positive for fentanyl or a fentanyl analogue increased from 3.0% (95% CI: 2.6-3.4%) in 2012-68.3% (67.7-68.9%) in 2022 (p < 0.001 for trend). The percentage of opioid-containing samples that were positive for fentanyl or a fentanyl analogue increased between 2012 and 2022 in all regions. In 2022, the percentage of samples containing fentanyl or an analogue followed an east-to-west gradient: 15.8% (13.3-18.6%) of samples in Atlantic Canada and 84.7% (83.6-85.7%) in British Columbia. Carfentanil was present in 4.9% (4.6-5.2%) of opioid-containing samples in Canada in 2022 and 19.7% (18.3-21.2%) of opioid-containing samples in Alberta. Conclusions: The illicit opioid supply in Canada increasingly contains toxic synthetic opioids. As of 2022, important regional differences existed in the illicit opioid supply in Canada.

Xylazine awareness, desire, use and exposure: Preliminary findings from the Rhode Island community-based drug checking cohort study.

Background: Xylazine is an ⍺2 adrenergic receptor agonist and a veterinary sedative that can cause severe health complications yet interventions to detect and treat human exposure remain underdeveloped. Community-based drug checking services (DCS) involve the testing of small amounts of drugs to increase community knowledge of unregulated supplies and decrease harms. This study characterized xylazine awareness, desire, use and exposure among people who use drugs (PWUD) in Rhode Island, US. Methods: We analyzed data from an ongoing PWUD cohort study. In 2023, 125 PWUD were enrolled and surveyed. Using point-of-care Fourier Transform infrared spectroscopy (FTIR-S), we tested a drug sample from each participant onsite and confirmed the results offsite at a laboratory. Results were conveyed in real-time, along with harm reduction education, referrals to resources and care. Results: Virtually all participants (99.2 %) wanted to avoid xylazine exposure. Half (51.2 %) knew what xylazine was, and a quarter (26.1 %) suspected previous exposure. Xylazine exposure was primarily surmised through sedating (45.2 %) and ulcerative (29.0 %) effects. Only 8.8 % of participants submitted a sample that they expected to contain xylazine. Xylazine was detected in 14.5 % of samples using FTIR-S and in 21.4 % of samples using a dual laboratory approach of gas chromatography mass spectrometry (GC-MS) and liquid chromatography quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS). Participants thought that these xylazine-positive samples were fentanyl (78.3 %), heroin (13.0 %), or Percocet® (8.7 %). Conclusion: Implementing point-of-care DCS at harm reduction organizations could be useful in rapidly increasing xylazine awareness and engaging at-risk individuals in prevention, harm reduction, treatment, and rapid care for xylazine-related wounds.

Reinforcing effects of fentanyl analogs found in illicit drug markets.

RATIONALE: The 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). OBJECTIVES: Here, 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. METHODS: Sprague-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. RESULTS: Self-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. CONCLUSIONS: Our work provides new evidence that FAs display significant abuse liability in male and female rats, which suggests the potential for compulsive use in humans.

Fentanyl and xylazine crisis: Crafting coherent strategies for opioid overdose prevention.

The United States is in the throes of a severe opioid overdose epidemic, primarily fueled by the pervasive use of fentanyl and the emerging threat of xylazine, a veterinary sedative often mixed with fentanyl. The high potency and long duration of fentanyl is compounded by the added risks from xylazine, heightening the lethal danger faced by opioid users. Measures such as enhanced surveillance, public awareness campaigns, and the distribution of fentanyl-xylazine test kits, and naloxone have been undertaken to mitigate this crisis. Fentanyl-related overdose deaths persist despite these efforts, partly due to inconsistent policies across states and resistance towards adopting harm reduction strategies. A multifaceted approach is imperative in effectively combating the opioid overdose epidemic. This approach should include expansion of treatment access, broadening the availability of medications for opioid use disorder, implementation of harm reduction strategies, and enaction of legislative reforms and diminishing stigma associated with opioid use disorder.

Structure-Activity Relationships of the Fentanyl Scaffold: Identification of Antagonists as Potential Opioid Overdose Reversal Agents.

Opioid-related overdoses account for almost half of all drug overdose deaths in the United States and cause more preventable deaths every year than car crashes. Fentanyl, a highly potent mu opioid receptor (MOR) agonist and its analogues (fentalogues) are increasingly found in illicit drug samples, both where the primary drug of abuse is an opioid and where it is not. The prevalence of fentalogues in the illicit drug market is thought to be the primary driver of the increased number of opioid-related overdose deaths since 2016. In fact, fentanyl and its analogues are involved in more than 70% of opioid-related overdoses. The standard opioid overdose rescue therapy naloxone is often insufficient to reverse opioid overdoses caused by fentalogue agonists under current treatment paradigms. However, the pharmacology of many fentalogues is unknown. Moreover, within the fentalogue series of compounds, it is possible that antagonists could be identified that might be superior to naloxone as opioid overdose reversal agents. In this report, we explore the pharmacology of 70 fentalogues and identify compounds that behave as MOR antagonists in vitro and demonstrate with one of these reversals of fentanyl-induced respiratory depression in the mouse. Such compounds could provide leads for the development of effective agents for the reversal of opioid overdose.

Temperature and pH-dependent stability of fentanyl analogs: Degradation pathways and potential biomarkers.

The collection, storage, and transport of samples prior to and during analysis is of utmost importance, especially for highly potent analogs that may not be present in high concentrations and are susceptible to pH or thermally mediated degradation. An accelerated stability study was performed on 17 fentanyl analogs (fentalogs) over a wide range of pH (2-10) and temperature (20-60°C) conditions over 24 h. Dilute aqueous systems were used to investigate temperature and pH-dependent kinetics using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Liquid chromatography-quadrupole/time-of-flight-mass spectrometry (LC-Q/TOF-MS) was used for structural elucidation of degradants. With the exception of remifentanil, all fentalogs evaluated were stable at pH 6 or lower. Fentalogs were generally unstable in strongly alkaline environments and at elevated temperatures. Remifentanil was the least stable drug and N-dealkylated fentalogs were the most stable. Fentanyl degraded to acetylfentanyl, norfentanyl, fentanyl N-oxide, and 1-phenethylpyridinium salt (1-PEP). A total of 26 unique breakdown products were observed for 15 of the fentanyl derivatives studied. Common degradation pathways involved N-dealkylation, oxidation of the piperidine nitrogen, and ß-elimination of N-phenylpropanamide followed by oxidation/dehydration of the piperidine ring. Ester and amide hydrolysis, demethylation at the propanamide, and O-demethylation were observed for selected fentalogs only. The potential for analyte loss should be considered during the pre-analytical phase (i.e., shipping and transport) where environmental conditions may not be controlled, as well as during the analysis itself.

Sex differences in sensitivity to fentanyl effects in mice: Behavioral and molecular findings during late adolescence.

PURPOSE: Sex differences play a crucial role in understanding vulnerability to opioid addiction, yet there have been limited preclinical investigations of this effect during the transition from adolescence to adulthood. The present study compared the behaviors of male and female rodents in response to fentanyl treatment and targeted molecular correlates in the striatum and medial prefrontal cortex. MATERIALS AND METHODS: Thirty adolescent C57BL/6J mice underwent a 1-week fentanyl treatment with an escalating dose. In addition to evaluating locomotor activity and anxiety-related parameters, we also assessed naloxone-induced fentanyl acute withdrawal jumps. We employed real-time quantitative PCR (qPCR) to assess overall gene expression of dopaminergic receptors (Drd1, Drd2, Drd4 and Drd5) and the µ-opioid receptor Oprm1. The levels of epigenetic base modifications including 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) were assessed on CpG islands of relevant genes. RESULTS: Females had higher locomotor activity than males after chronic fentanyl treatment, and they exhibited higher fentanyl withdrawal jumping behavior induced by naloxone. Females also presented lower Drd4 gene expression and DNA methylation (5mC + 5hmC) in the striatum. We found that locomotor activity and fentanyl withdrawal jumps were negatively correlated with Drd4 methylation and gene expression in the striatum, respectively. CONCLUSIONS: The findings suggested that female mice displayed heightened sensitivity to the effects of fentanyl treatment during the transition from adolescence to adulthood. This effect may be associated with molecular alterations related to the Drd4 gene.

Case report of pharmacokinetic analysis of continuous intravenous infusion of fentanyl in a patient with severe burn: burn shock stage complicates pain management.

BACKGROUND: Fentanyl is widely used as an analgesic and sedative for patients with severe burn injuries in intensive care units. However, pharmacokinetic (PK) data for fentanyl, particularly for continuous intravenous infusion during the acute phase of burn injuries, are limited. Here, we report the clinical course and changes in blood fentanyl concentrations during the acute phase in a patient with severe burns treated with continuous intravenous infusion of fentanyl. CASE PRESENTATION: A woman in her 40s, with burns caused by a gas cylinder explosion, was transported to our hospital. The patient had burn wounds on face, neck, shoulders, and all four extremities, with a total burn area of 39.0%. For pain relief, the patient received a continuous infusion of 0.01 mg/mL fentanyl (20-30 µg/h) with a target blood concentration of 1.0-1.5 ng/mL, but continued to suffer from pain due to burning during the acute phase. We measured the blood fentanyl concentrations and found that all concentrations obtained during the acute phase were subtherapeutic. Notably, during the burn shock stage, blood concentrations of fentanyl were 0.50 ng/mL on day 1 and 0.66 ng/mL on day 2, indicating that the blood concentration did not rise sufficiently for the dosage. From days 0 to 2, the patient was administered a massive fluid load for burn shock. After the burn shock stage resolved, fentanyl concentrations gradually approached the target range, and the pain rating scale improved, even though the fentanyl administration rate remained unchanged (30 µg/h). CONCLUSIONS: Major changes in the fluid volumes of body compartments that occur with large burns might increase the volume of fentanyl distribution, thereby lowering its concentration when a standard dose is administered. Our findings indicate that the PK of fentanyl in patients with severe burns can be substantially affected, especially during the shock phase, implying the importance of titrating analgesics for clinical efficacy in the acute phase.

Submersible voltammetric sensing probe for rapid and extended remote monitoring of opioids in community water systems.

The intensifying global opioid crisis, majorly attributed to fentanyl (FT) and its analogs, has necessitated the development of rapid and ultrasensitive remote/on-site FT sensing modalities. However, current approaches for tracking FT exposure through wastewater-based epidemiology (WBE) are unadaptable, time-consuming, and require trained professionals. Toward developing an extended in situ wastewater opioid monitoring system, we have developed a screen-printed electrochemical FT sensor and integrated it with a customized submersible remote sensing probe. The sensor composition and design have been optimized to address the challenges for extended in situ FT monitoring. Specifically, ZIF-8 metal-organic framework (MOF)-derived mesoporous carbon (MPC) nanoparticles (NPs) are incorporated in the screen-printed carbon electrode (SPCE) transducer to improve FT accumulation and its electrocatalytic oxidation. A rapid (10 s) and sensitive square wave voltammetric (SWV) FT detection down to 9.9 µgL-1 is thus achieved in aqueous buffer solution. A protective mixed-matrix membrane (MMM) has been optimized as the anti-fouling sensor coating to mitigate electrode passivation by FT oxidation products and enable long-term, intermittent FT monitoring. The unique MMM, comprising an insulating polyvinyl chloride (PVC) matrix and carboxyl-functionalized multi-walled carbon nanotubes (CNT-COOH) as semiconductive fillers, yielded highly stable FT sensor operation (> 95% normalized response) up to 10 h in domestic wastewater, and up to 4 h in untreated river water. This sensing platform enables wireless data acquisition on a smartphone via Bluetooth. Such effective remote operation of submersible opioid sensing probes could enable stricter surveillance of community water systems toward timely alerts, countermeasures, and legal enforcement.

Tropine exacerbates the ventilatory depressant actions of fentanyl in freely-moving rats.

Our lab is investigating the efficacy profiles of tropine analogs against opioid-induced respiratory depression. The companion manuscript reports that the cell-permeant tropeine, tropine ester (Ibutropin), produces a rapid and sustained reversal of the deleterious actions of fentanyl on breathing, alveolar-arterial (A-a) gradient (i.e., index of alveolar gas exchange), and arterial blood-gas (ABG) chemistry in freely-moving male Sprague Dawley rats, while not compromising fentanyl analgesia. We report here that in contrast to Ibutropin, the injection of the parent molecule, tropine (200 µmol/kg, IV), worsens the adverse actions of fentanyl (75 µg/kg, IV) on ventilatory parameters (e.g., frequency of breathing, tidal volume, minute ventilation, peak inspiratory and expiratory flows, and inspiratory and expiratory drives), A-a gradient, ABG chemistry (e.g., pH, pCO2, pO2, and sO2), and sedation (i.e., the righting reflex), while not affecting fentanyl antinociception (i.e., the tail-flick latency) in freely-moving male Sprague Dawley rats. These data suggest that tropine augments opioid receptor-induced signaling events that mediate the actions of fentanyl on breathing and alveolar gas exchange. The opposite effects of Ibutropin and tropine may result from the ability of Ibutropin to readily enter peripheral and central cells. Of direct relevance is that tropine, resulting from the hydrolysis of Ibutropin, would combat the Ibutropin-induced reversal of the adverse effects of fentanyl. Because numerous drug classes, such as cocaine, atropine, and neuromuscular blocking drugs contain a tropine moiety, it is possible that their hydrolysis to tropine has unexpected/unintended consequences. Indeed, others have found that tropine exerts the same behavioral profile as cocaine upon central administration. Together, these data add valuable information about the pharmacological properties of tropine.

Fentanyl-Related Deaths in Ontario, Canada: Toxicological Findings and Circumstances of Death in 4395 Cases (2020-2022).

Over the last 20 years there has been a significant increase in fentanyl related deaths in Ontario, Canada. This report examines toxicological findings in a series of death investigations in which fentanyl was quantitated to identify the prevalence, trends and demographic data associated with fentanyl in Ontario, Canada, and to highlight the changes in these trends since fentanyl began appearing in casework in Ontario in the early 2000s. A retrospective study of all cases in which fentanyl was quantitated in blood, using liquid chromatography-tandem mass spectrometry, was conducted for the time period between January 1, 2020, and December 31, 2022. A total of 4395 cases were included, 77% of the decedents were male and 23% were female with ages ranging from 0 to 95. The most frequently classified cause of death was mixed drug toxicity (69%) followed by fentanyl intoxication at 19%. Less than 10% of cases where fentanyl was quantitated were classified as non-drug related deaths. Fentanyl concentrations in all cases ranged from 1.3 to > 2000 ng/mL. Other drugs were frequently detected with fentanyl. In mixed drug toxicity cases, stimulants were the most frequently encountered class of drugs: cocaine was identified in 51.8% and methamphetamine was observed in 43.0% of cases, respectively. Detailed reports for select cases were included to provide additional insight into the different case types and to show the difficulty in interpreting blood concentrations without additional detailed case histories. This study provides valuable information for the scientific and medical community regarding the continued use of fentanyl and how patterns of fentanyl use have evolved since it began to appear in forensic casework.