Sex Differences in the Development of an Opioid Addiction-Like Phenotype: A Focus on the Telescoping Effect.

Background: Women develop addiction and drug-related health consequences after fewer years of drug use than men; this accelerated time course, or telescoping effect, has been observed clinically for multiple drugs, including opioids. Preclinical studies indicate that this is a biologically based phenomenon; however, these studies have focused exclusively on cocaine, and none have considered health effects. Methods: In this study, we used a rat (Sprague Dawley) model to determine sex differences in the time course for the development of an opioid addiction-like phenotype, as defined by the development of physical dependence (withdrawal-induced weight loss) and an increase in motivation for fentanyl (under a progressive-ratio schedule). Effects were determined following either 10 days (optimized, experiment 1) or 3 days (threshold, experiment 2) of extended-access fentanyl self-administration (24 hours/day, fixed ratio 1, 2- to 5-minute trials/hour) or following short-access fentanyl self-administration (subthreshold, experiment 3; fixed ratio 1, up to 40 infusions/day). Opioid-related adverse health effects were also determined (experiment 4). Results: Motivation for fentanyl was similarly increased in males and females following 10 days of extended-access self-administration (experiment 1), was transiently increased in females, but not males, following 3 days of extended-access self-administration (experiment 2) and was not increased in either sex following short-access self-administration (experiment 3). Females developed fentanyl-associated adverse health effects more readily than males (experiment 4), with particularly robust differences during extended-access self-administration and withdrawal. Conclusions: As with findings in humans, female rats developed opioid addiction-like features and adverse health consequences more readily than male rats. These data provide support for a biologically based telescoping effect in females for opioids, particularly for opioid-related adverse health consequences.

In this issue, we explore how female rats develop signs of opioid addiction and related health issues faster than male rats, a phenomenon known as the telescoping effect. This study expands on previous research by using a rat model to assess addiction-like behaviors and health consequences following different withdrawal period and durations of fentanyl self-administration. The findings underline the biological underpinnings of sex differences in addiction trajectories, previously demonstrated in humans but not yet studied in opioids until now.

How substance use preferences and practices relate to fentanyl exposure among people who use drugs in Rhode Island, USA.

Background: Over 107,000 people died in the United States (U.S.) from drug overdose in 2022, with over one million overdose deaths since 1999. The U.S. drug market is characterized by a highly toxic, unregulated, and rapidly changing supply. Understanding the extent of exposure to fentanyl among people who use drugs (PWUD) will guide public health interventions aimed to decrease overdose. Methods: We utilized baseline data from the Rhode Island Prescription and Illicit Drug Study, a randomized controlled trial of harm reduction-oriented interventions for PWUD in Rhode Island from 2020 to 2023. We evaluated sociodemographic and drug use-related covariates and examined fentanyl presence in urine drug testing (UDT). We built a classification and regression tree (CART) model to identify subpopulations with the highest likelihood of fentanyl presence in UDT. Results: Among 446 participants, those with fentanyl present in UDT tended to be younger, non-Hispanic white, and had recently injected drugs (p<0.05 for all). The CART analysis demonstrated a large variation in sample sub-groups' likelihood of fentanyl presence in UDT, from an estimated probability of 0.09 to 0.90. Expected recent fentanyl exposure was the most important predictor of fentanyl in UDT. Conclusions: Univariate analyses and CART modeling showed substantial variation in the presence of fentanyl in UDT among PWUD. Harm reduction services for people actively injecting drugs and drug checking programs based on capacity-building, empowerment, and targeted towards those not yet engaged in services are urgently needed to support PWUD in navigating the current volatile drug supply.

Trends in opioid exposures among young children reported to United States poison centers from 2016 to 2023.

INTRODUCTION: The objective of this study was to update and expand on previous studies of opioid exposures among young children reported to America's Poison Centers, and to describe how fentanyl and medications for opioid use disorder have contributed. METHODS: This retrospective study investigated 34,632 reports of single-substance opioid exposure from 2016 to 2023 involving pediatric patients aged one month to six years old. Descriptive statistics, tests for data normality, and significance testing were performed where applicable. RESULTS: Of 34,632 reported exposures, 96.7% were unintentional. The median age of exposure was 2.0 years (IQR 1.33-3.0 years). Reported exposures decreased by 57.5% over the study period (r = -0.96; P < 0.001). However, there was a 300% absolute increase in deaths and major effects (r = 0.96; P < 0.001). Exposures resulting in minor, no effect, not followed, or unable to follow decreased 66.2% (r = -0.99; P < 0.001). Buprenorphine was most frequently involved, comprising 23.4% of reported exposures. Buprenorphine (OR 1.93; P < 0.001) and methadone (OR 14.98; P < 0.001) were associated with an increased risk of severe effects when compared to other prescription drugs (OR: 1). There was an absolute increase of 512% over time in reports of heroin, fentanyl, synthetic non-pharmaceutical opioids (r = 0.92; P < 0.001), which were also associated with severe effects (OR 20.1; P < 0.001). DISCUSSION: Pediatric opioid exposures have previously been reported to be relatively stable. It is likely the 57.5% reduction is exaggerated due to underreporting from health care providers. However, decreases in exposures are presumed to be balanced throughout the dataset and, therefore, without differential impact on other points of analysis. Our study highlights the continued need for enhanced poisoning prevention strategies. CONCLUSIONS: The relative severity of poisonings reported to poison centers worsened over the study period. The opioids implicated have shifted away from hydrocodone, oxycodone, and tramadol, and towards fentanyl and buprenorphine.

Biological sex modulates the efficacy of 2,5-dimethoxy-4-iodoamphetamine (DOI) to mitigate fentanyl demand.

BACKGROUND: Overdose deaths remain high for opioid use disorder, emphasizing the need to pursue innovative therapeutics. Classic psychedelic drugs that engage many monoamine receptors mitigate opioid use. Here, we tested the hypothesis that the preferential serotonin 5-HT2AR agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI) could reduce the demand for fentanyl in a preclinical model of fentanyl self-administration. METHODS: Male and female Sprague-Dawley rats (n = 25-29) were implanted with indwelling jugular catheters and allowed to self-administer fentanyl (3.2µg/kg/infusion). Rats progressed to a novel low price twice within-session threshold procedure where rats sampled the lowest price twice before decreasing the dose of fentanyl by a » log every 10minutes across 11 doses. Once stable, rats were pretreated with saline or DOI (0.01, 0.03, 1mg/kg). Fentanyl consumption was analyzed using an exponentiated demand function to extract the dependent variables, Q0 and α. RESULTS: Male and female rats acquired fentanyl self-administration in the lowest price twice within-session threshold procedure. DOI dose-dependently altered fentanyl intake such that 5-HT2AR activation decreased Q0 in female rats but increased Q0 in male rats. For demand elasticity, DOI increased α in male rats but did not alter α in female rats. DOI did not alter inactive lever presses or latency. CONCLUSION: DOI reduces consumption at minimally constrained costs but did not affect the reinforcement value of fentanyl in female rats. Alternatively, DOI significantly reduced the reinforcement value of fentanyl in male rats. Biological sex alters the therapeutic efficacy of DOI and 5-HT2AR activation sex-dependently alters opioid reinforcement.

Anxiety and risk-taking behavior maps onto opioid and alcohol polysubstance consumption patterns in male and female mice.

Polysubstance use is prevalent in the population but remains understudied in preclinical models. Alcohol and opioid polysubstance use is associated with negative outcomes, worse treatment prognosis, and higher overdose risk; but underlying mechanisms are still being uncovered. Examining factors that motivate use of one substance over another in different contexts in preclinical models will better our understanding of polysubstance use and improve translational value. Here we assessed baseline anxiety-like and locomotive behavior and then measured voluntary consumption of multiple doses of alcohol and fentanyl in group housed male and female mice using our novel Socially Integrated Polysubstance (SIP) system. Fifty-six male (n=32) and female (n=24) adult mice were housed in groups of 4 for one week with continuous access to food, water, two doses of ethanol (5% and 10%) and two doses of fentanyl (5 ug/ml and 20 ug/ml). Our analyses revealed sex differences across multiple domains - female mice consumed more liquid in the dark cycle, had higher activity, a higher preference for both ethanol and fentanyl over water, and their fentanyl preference increased over the seven days. We then used machine-learning techniques to reveal underlying relationships between baseline behavioral phenotypes and subsequent polysubstance consumption patterns, where anxiety-and risk-taking-like behavioral phenotypes mapped onto discrete patterns of polysubstance use, preference, and escalation. By simulating more translationally relevant substance use and improving our understanding of the motivations for different patterns of consumption, this study contributes to the developing preclinical literature on polysubstance use with the goal of facilitating better treatment outcomes and novel therapeutic strategies.

Dopamine D2 receptors in the accumbal core region mediates the effects of fentanyl on sleep-wakefulness.

Fentanyl, a potent analgesic and addictive substance, significantly impacts sleep-wakefulness (S-W). Acutely, it promotes wake, whereas chronic abuse leads to severe sleep disruptions, including insomnia, which contributes to opioid use disorders (OUD), a chronic brain disease characterized by compulsive opioid use and harmful consequences. Although the critical association between sleep disruptions and fentanyl addiction is acknowledged, the precise mechanisms through which fentanyl influences sleep remain elusive. Recent studies highlight the role of the dopaminergic system of the nucleus accumbens (NAc) in S-W regulation, but its specific involvement in mediating fentanyl's effects on S-W remains unexplored. We hypothesized that dopamine D2 receptors mediate fentanyl-induced effects on S-W. To test this hypothesis, male C57BL/6J mice, instrumented with sleep recording electrodes and bilateral guide cannulas above the accumbal core region (NAcC), were utilized in this study. At dark onset, animals were bilaterally administered sulpiride (D2 receptors antagonist; 250 ng/side) in the NAcC followed by an intraperitoneal injection of fentanyl (1.2 mg/Kg). S-W was examined for the next 12 h. We found that systemic administration of fentanyl significantly increased wakefulness during the first 6 h of the dark which was followed by a significant increase in NREM and REM sleep during the second 6 h of the dark period. D2-receptor blockade significantly reduced this effect as evidenced by a significant reduction in fentanyl-induced wakefulness during first 6 h of dark period and sleep rebound during the second 6 h. Our findings suggest that D2 receptors in the NAcC plays a vital role in mediating the fentanyl-induced changes in S-W.

Self-Reported Illicitly Manufactured Fentanyl Use and Associated Health and Substance Use Risks in the United States, 2022.

OBJECTIVE: Illicitly manufactured fentanyl (IMF) has emerged as a catalyst of the recent drug epidemic in the United States. To devise more targeted and effective prevention and treatment strategies, it is crucial to understand the demographics of the population who consumes IMF and their health and associated substance use risks. Therefore, this study explores the sociodemographic characteristics, health diagnoses, and drug injection practices of individuals reporting IMF use. METHODS: Data were derived from the 2022 National Survey on Drug Use Health, based on a nationally representative sample of non-institutionalized individuals aged 12 and older in the United States. Focusing on 306 adults who reported ever using IMF, we examined their sociodemographic characteristics, health diagnoses, and substance-related behaviors in comparison to adults with a drug use disorder who did not report IMF use, using logistic regression analyses. RESULTS: The majority of U.S. adults reporting IMF use were aged 35-64, male, non-Hispanic White, with a high school education or lower, never married, and had an annual household income below $40,000. Compared to adults with a drug use disorder who did not report IMF use, they were more likely to report heart conditions (AOR = 2.67, 95% CI = 1.29-5.54) and Hepatitis B or C (AOR = 8.35, 95% CI = 4.05-17.02). Nearly half of this group had an opioid use disorder (OUD) in the past year, and 65.7% (95% CI = 56.7-74.8) reported a history of injecting drugs. CONCLUSIONS: To effectively curb the current drug epidemic, incorporating effective treatment for OUD and harm reduction strategies is crucial.

Associations with early vomiting when using intranasal fentanyl and nitrous oxide for procedural sedation in children: A secondary analysis of a randomised controlled trial.

OBJECTIVE: Intranasal (IN) fentanyl and nitrous oxide (N2O) can be combined to provide procedural sedation and analgesia to children. This combination is advantageous because of rapid onset of action and non-parenteral administration, but is associated with increased vomiting. We sought to describe the associations of demographic and procedural factors with early vomiting when using this combination in children. METHODS: This was a planned secondary analysis of a randomised controlled trial comparing the effect of oral ondansetron versus placebo at a single paediatric hospital. Children aged 3 to <18 years with planned procedural sedation with IN fentanyl and N2O were randomised to receive oral ondansetron or placebo prior to N2O administration. Vomiting was defined as early if occurring during or up to 1 h after N2O delivery. We assessed the relationship between early vomiting, demographic and procedural characteristics. RESULTS: Participants were recruited between October 2016 and January 2019 and 62 out of 436 (14%) had early vomiting. The risk of early vomiting was 30% higher with higher total dose of fentanyl, risk ratio = 1.3 (95% confidence interval = 1.004-1.59). There was little evidence of a relationship between the occurrence of early vomiting and sex, age, weight, type of procedure, fasting duration, time between fentanyl administration and start of procedure, and procedure duration. CONCLUSION: We found that higher doses of IN fentanyl were associated with higher risk of early vomiting when administered with N2O in children. Other factors did not appear to be associated with vomiting.

Correlates of fentanyl preference among people who use drugs in Rhode Island.

BACKGROUND: Fentanyl is increasingly pervasive in the unregulated drug supply and is a driver of drug overdose deaths in the United States. The aims of this study were to characterize and identify correlates of fentanyl preference among people who use drugs (PWUD) in Rhode Island (RI). METHODS: Using bivariate analysis, we examined associations between fentanyl preference and sociodemographic and psychosocial characteristics at baseline among participants enrolled in the RI Prescription Drug and Illicit Drug Study from August 2020-February 2023. Fentanyl preference was operationalized based on responses to a five-point Likert scale: "I prefer using fentanyl or drugs that have fentanyl in them." Participants who responded that they "strongly disagree," "disagree," or were "neutral" with respect to this statement were classified as not preferring fentanyl, whereas participants who responded that they "agree" or "strongly agree" were classified as preferring fentanyl. RESULTS: Among 506 PWUD eligible for inclusion in this analysis, 15% expressed a preference for fentanyl or drugs containing fentanyl as their drug of choice. In bivariate analyses, preference for fentanyl was positively associated with younger age, white race, lifetime history of overdose, history of injection drug use, past month enrollment in a substance use treatment program, past month treatment with medications for opioid use disorder, and preferences for heroin and crystal methamphetamine (all p < 0.05). Descriptive data yielded further insight into reasons for fentanyl preference, the predominant having to do with perceived effects of the drug and desire to avoid withdrawal symptoms. CONCLUSIONS: Only a relatively small subset of study participants preferred drugs containing fentanyl. Given the increased prevalence of fentanyl contamination across substances within the unregulated drug market, the result for PWUD is increasingly less agency with respect to choice of drug; for example, people may be forced to use fentanyl due to restricted supply and the need to mitigate withdrawal symptoms, or may be using fentanyl without intending to do so. Novel and more effective interventions for PWUD, including increased access to age-appropriate harm reduction programs such as fentanyl test strips and overdose prevention centers, are needed to mitigate fentanyl-related harms.

Comparison of the reinforcing, antinociceptive, and respiratory depressant effects of prototypical and G-protein biased mu-opioid receptor agonists in male and female Sprague-Dawley rats.

RATIONALE: G-protein biased mu-opioid receptor (MOR) agonists have been reported to exhibit superior therapeutic windows compared to prototypical MOR agonists when relating antinociception to respiratory depression. However, there is relatively little research on the abuse potential of G-protein biased MOR agonists in relation to other behavioral endpoints. OBJECTIVES: The aim of the present study was to quantitatively compare the reinforcing, antinociceptive, and respiratory-depressant effects of the prototypical MOR agonists, fentanyl and oxycodone, to the G-protein biased MOR agonists, SR14968 and SR17018, in male and female rats. METHODS: In the self-administration study, four separate groups of Sprague-Dawley (SD) rats self-administered intravenous (i.v.) fentanyl, oxycodone, SR14968, and SR17018 under a progressive-ratio schedule of reinforcement. Using a within-subjects design, separate cohorts of SD rats were tested with i.v. fentanyl, oxycodone, SR14968, and SR17018 using a hot-plate assay, assays of neuropathic and inflammatory antinociception, and whole-body plethysmography. RESULTS: All MOR agonists functioned as reinforcers, but SR14968 and SR17018 were less efficacious relative to oxycodone and fentanyl. Moreover, all MOR agonists produced dose-dependent and fully efficacious antinociception across all nociception modalities. Oxycodone and fentanyl, but not SR14968 or SR17018, produced respiratory depression in a dose-dependent manner. CONCLUSION: The present results indicate that the G-protein biased MOR agonists tested herein produce MOR-typical antinociception, exhibit reduced but apparent abuse potential, and do not produce respiratory effects at doses that are above the antinociceptive range. Atypical MOR agonists within the SR series should be further studied as foundational molecules for the development of safter analgesics.

Increasing Prevalence of Xylazine and Worsening Upper-Extremity Wounds in Injection Drug Use: A Local Phenomenon With National Implications.

The rising presence of xylazine in Philadelphia's fentanyl supply has led to various upper-extremity complications in individuals who inject drugs. Sociogeographic trends predict that our current local phenomenon will spread nationally. We aim to discuss the drug's impact on clinical presentation and patient care via a cohort of five patients with upper-extremity wounds related to drug use. Interventions included local wound care, revascularization, compartment release, free flap reconstruction, and amputation. Successful treatment of these patients, who are often in challenging psychosocial environments, requires an individualized and interdisciplinary approach including surgical services, infectious disease, wound care, addiction medicine, psychiatry, social services, and prosthetic services.

Prevalence and correlates of fentanyl test strip use among people who use drugs in Rhode Island.

BACKGROUND: Illicitly manufactured fentanyl accounts for a majority of overdose fatalities in the US. Research has demonstrated that fentanyl test strips (FTS) help people who use drugs (PWUD) avoid unintended exposure to fentanyl and overdose. This study assesses characteristics associated with FTS use among PWUD in Rhode Island. Such findings may shed light on whether there are subgroups of PWUD who are less likely to be using FTS and therefore may benefit from their use. METHODS: From September 2020 - February 2023, participants were recruited to participate in RAPIDS, a clinical trial assessing whether FTS provision can reduce overdose rates. Baseline data were used to assess correlates of lifetime FTS use through bivariable and multivariable analyses. We also examined drug testing patterns relating to FTS use in the past month. RESULTS: Of 509 people enrolled, 376 (73.9 %) had heard of FTS before enrollment. Among this group, 189 (50.3 %) reported lifetime FTS use and 98 (26.1 %) reported use in the last month. In bivariable analyses, lifetime injection drug use, responding to an overdose, and drug selling were associated with FTS use. Solitary drug use was not associated with FTS uptake. In the multivariable analysis, gender and lifetime naloxone administration were associated with FTS use. Of those who used FTS in the past month, 76.5 % had at least one test that was positive for fentanyl. CONCLUSIONS: We found high uptake of FTS use among PWUD in Rhode Island. Our results also suggest a need for targeted outreach to increase FTS uptake among sub-groups of PWUD. CLINICAL TRIAL REGISTRATION: The Rhode Island Prescription and Illicit Drug Study is a registered clinical trial, NCT043722838.

Effects of xylazine on naloxone-precipitated fentanyl withdrawal in male and female rats.

PURPOSE: The combination of fentanyl and xylazine (i.e., "tranq-dope") was recently declared an emerging national health threat in the United States. Given the recency of this development, very little is known regarding the behavioral pharmacology of fentanyl-xylazine combinations. The purpose of this study was to characterize the somatic and affective withdrawal symptoms of this drug combination. METHODS: Male and female Long Evans rats were given twice daily (08:00 and 20:00) subcutaneous injections of fentanyl, xylazine, or combined fentanyl-xylazine for five days. On the sixth (testing) day, rats were given a final injection at 08:00. Four hours later, rats were injected intraperitoneally with either saline or a naloxone challenge before behavioral observation. Somatic withdrawal was examined using the Gellert-Holtzman scale and anxiety-like behavior was examined using the elevated plus maze. RESULTS: Naloxone administration did not induce somatic or affective symptoms in rats treated with fentanyl alone, a low dose of xylazine alone, or a high dose of xylazine alone. Naloxone induced somatic but not affective withdrawal symptoms in rats treated with both fentanyl and xylazine. CONCLUSION: Chronic co-exposure to fentanyl and xylazine produces an opioid-like somatic withdrawal syndrome at doses that are not apparent with either drug alone. These results corroborate clinical reports that xylazine worsens fentanyl withdrawal and suggest that novel interventions may be required to treat withdrawal from fentanyl-xylazine combinations in humans.

Synthetic opioids in Poland-A cause for concern or a media distraction?

BACKGROUND: The North American continent has been battling a major health crisis defined by opioids like OxyContin and fentanyl for over two decades now. In that time, it seemed that Europe is rather resilient to a similar problem, and heroin retained its position as a the most problematic opioid. This does seem to be changing and European media, including in Poland, is starting to report on growing popularity of synthetic opioids like fentanyl. METHODS: We use official data showing the number of prescriptions for synthetic opioids; data showing the percentage of people entering treatment due to different opioids; police data on drug interceptions as well as lab closures, and data on opioid related poisonings. RESULTS: The data demonstrates that although Polish physicians are increasingly more likely to prescribe synthetic opioids like OxyContin or Fentanyl, their problematic use remains low. CONCLUSION: Poland currently does not seem to be in a position that resembles an early stage of an opioid crisis. With this article we want to calm a heated public debate that is currently taking place in Poland, and redirect attention to a much more substantial problem of synthetic cathinones.

Collateral Damage: Neurological Correlates of Non-Fatal Overdose in the Era of Fentanyl-Xylazine.

Non-fatal opioid overdoses are associated with significant morbidity. Hypoxic brain injury caused by opioid-induced respiratory depression is a key mechanism of such morbidity. For example, reports describe an amnestic syndrome in opioid users associated with acute injury to the hippocampus, a brain region that is highly susceptible to hypoxic injury. In our recent study we investigated the effects of non-fatal opioid overdose on the hippocampal volume in a well-characterized sample of opioid use disorder (OUD) patients with a history of overdose (OD) compared to those with no prior overdose (NOD). Using structural magnetic resonance imaging (MRI) and voxel-based morphometry, we observed lower hippocampal volume in patients with a history OD than in the NOD group. These findings support an association between non-fatal opioid overdose and hippocampal injury, which we hypothesize contributes to recently reported cases of OUD related amnestic syndrome. Here we review our study findings and the potential pathophysiological mechanisms underlying the acute and delayed hippocampal injury in nonfatal opioid overdose. We also discuss the implications for the risk of overdose and brain injury with the increased prevalence of fentanyl and xylazine contamination of the illicit opioid supply. Lastly, we highlight considerations for clinical management of the underappreciated neurological injury and cognitive dysfunction in OUD patients.

Effect of secondary and tertiary wastewater treatment methods on opioids and the subsequent environmental impact of effluent and biosolids.

Opioids are widely distributed, potent prescription analgesics that are known to be diverted for illicit use. Their prevalence of use is reflected by high concentrations of parent compounds and/or metabolites found in samples collected from wastewater treatment plants. Given that treatment byproducts enter the environment through several routes, the consequences of insufficient removal by treatment methods include unwanted environmental exposure and potential to disrupt ecosystems. Activated sludge treatment has been widely investigated for a large suite of prescription opioids but the same cannot be said for UV and chlorination. Additionally, the biosolid cycle of opioids has been overlooked previously. This study aimed to determine the extent to which secondary and tertiary wastewater treatment methods remove opioids from influent, and the associated environmental exposure for those persistent, as well as the fate of opioids in biosolids. Membrane bioreactor treatment proved effective for natural and semi-synthetic opioids while the effect of UV treatment was negligible. Chlorination was the most effective treatment method resulting in effluent with concentrations below theoretical predicted no-effect concentration. Biosolids are not subjected to any additional biological or chemical treatment after membrane bioreactor treatment and the levels detected in biosolid used as fertiliser had several opioids at potentially hazardous concentrations, indicated by a QSAR theoretical model. This data indicates a potential issue regarding the treatment process of biosolids and reliance on chlorination for effluent treatment that should be investigated in other treatment plants.

Identification of fentanyl analogs and potential biomarkers in urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-quadrupole/time of flight mass spectrometry (LC-Q/TOF-MS).

Novel synthetic opioids are a class of drugs abused for their potent analgesic effect and are responsible for many fatal intoxications, particularly within the United States. A targeted assay was developed and validated using LC-MS/MS, capable of identifying nineteen fentalogs. Solid phase extraction was used to isolate analytes of interest from urine. Limits of detection ranged from 0.05 to 0.1 ng/mL and the limit of quantitation was 0.5 ng/mL. Extraction efficiencies using the optimized procedure were 77-88 % for all targeted species. Bias, precision, matrix effects and interferences were within acceptable thresholds for all analytes. The validated assay was used to identify analytes of interest from thirty-seven individuals that had used fentanyl and related substances. In addition to quantitative analyses, a non-targeted liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q/TOF-MS) assay was also used to identify additional substances and potential biomarkers. Additional N-oxide and N-dealkylated species were identified using this approach, and the potential for biomarker use is presented, given the stability of some analytes within this class.

Structural Insight on Interaction of NMDA receptor with fentanyl, ketamine and Isoflurane: A Computational Study to Unravel Mode of Binding.

NMDA receptors are considered targets for many anesthetics if they are modulated by the drugs at clinically relevant concentrations. Volatile anesthetics like isoflurane and ketamine interact with NMDA receptors, inhibiting channel activation and thus blocking NMDA neurotransmission at clinically relevant concentrations. The mode of binding of commonly used drugs like ketamine, isoflurane, and fentanyl is poorly understood. We used molecular docking, molecular dynamics simulations, and DFT calculation of these drugs against the NMDA receptor. Using well-defined computational methods, we identified that these drugs have high docking scores and significant interaction with receptors. These drugs bind to the substrate-binding pocket and form a remarkable number of interactions. We have found that these interactions are stable and have low HOMO-LUMO energy gaps. This study provides enough evidences of strong and stable interaction between drugs and NMDA receptor.

Fentanyl and Sudden Death-A Postmortem Perspective for Diagnosing and Predicting Risk.

Sudden, unexpected deaths are extremely difficult for families, especially when the victim is a child. Most sudden deaths occur due to cardiovascular issues, and a smaller number (approximately one-quarter) are attributed to other causes, such as epilepsy. The medicinal and non-medicinal use of the synthetic opioid fentanyl, which can cause breathing problems, is frequently involved in these deaths. It is also being found more often in autopsies of sudden death cases, and the number of overdose deaths from illicit drugs containing fentanyl is increasing. There are cases in which it is mixed with other drugs. A gene known as the KCNH2 gene or human ether-a-go-go-related gene (hERG), involved in the heart's electrical activity, can be related to abnormal heart rhythms. This gene, along with others, may play a role in sudden deaths related to fentanyl use. In response, we have examined the scientific literature on genetic variations in the KCNH2 gene that can cause sudden death, the impact of fentanyl on this process, and the potential benefits of genetic testing for the victims to offer genetic counseling for their family members.