The role of take-home naloxone in the epidemic of opioid overdose involving illicitly manufactured fentanyl and its analogs

Naloxone Use in Novel Potent Opioid and Fentanyl Overdoses in Emergency Department Patients

Importance

Synthetic opioids, such as the fentanyl analogue and nitazene drug class, are among the fastest growing types of opioids being detected in patients in the emergency department (ED) with illicit opioid overdose (OD). However, clinical outcomes from OD of novel potent opioids (NPOs), specifically nitazenes, are unknown aside from small case series.

Objective

To determine naloxone administration and clinical sequelae of patients who were in the ED with NPO overdose compared with fentanyl OD.

Design, Setting, and Participants

This is a cohort study subgroup analysis of adults admitted to the ED and tested positive for NPOs among in the ongoing nationwide ToxIC Fentalog cohort study from 2020 to 2022. Patients who were in the ED with a presumed acute opioid OD and residual blood samples were included, and those testing positive for NPOs were analyzed. Patients were included in this analysis if their confirmatory testing was positive for an NPO analyte, such as brorphine, isotonitazene, metonitazene, and/or N-piperidinyl etonitazene. A comparison group included patients that were positive for fentanyl and devoid of any other analytes on toxicologic analysis.

Exposures

Patients were exposed to NPOs, including brorphine, isotonitazene, metonitazene and/or N-piperidinyl etonitazene.

Main Outcomes and Measures

The primary outcome was the total number of naloxone doses and total cumulative naloxone dose administered as part of routine clinical care following the OD. Naloxone requirements and clinical sequelae of NPO-positive patients were compared with those testing positive for fentanyl only.

Results

During the study period, 2298 patients were screened, of whom 717 met inclusion criteria, 537 had complete laboratory testing data, with 11 (2.0%) positive for only fentanyl and 9 (1.7%) positive for NPOs (brorphine, isotonitazene, metonitazene, or N-piperidinyl etonitazene). The age range of patients was aged 20 to 57 years (4 males [44.4%] and 5 females [55.6%]). The NPO group received a statistically significantly higher mean (SD) number of naloxone boluses in-hospital (1.33 [1.50]) compared with the fentanyl group (0.36 [0.92]) (P = .02), which corresponded to a moderately large effect size (Cohen d = 0.78). Metonitazene overdose was associated with cardiac arrest and more naloxone doses overall. Metonitazene cases had a mean (SD) number of 3.0 (0) naloxone doses, and 2 of 2 patients (100%) with metonitazene overdoses were administered cardiopulmonary resuscitation.

Conclusions and Relevance

In this cohort study of patients admitted to the ED with confirmed opioid overdose testing positive for NPOs, in-hospital naloxone dosing was high compared with patients who tested positive for fentanyl alone. Further study is warranted to confirm these preliminary associations.

Non-fentanyl new synthetic opioids - An update

BACKGROUND

New synthetic opioids (NSO) constitute one of the fastest-growing group of New Psychoactive Substances, which emerged on the illicit drug marker in the second half of 2000's. The most popular and the largest NSO subgroup are high potency fentanyl and its analogs. Subsequent to core-structure scheduling of fentanyl-related substances many opioids with different chemical structures are now emerging on the illicit drug market, rendering the landscape highly complex and dynamic.

METHODS

PubMed, Scopus and Google Scholar were searched for appropriate articles up to December 2022. Moreover, a search for reports was conducted on Institutional websites to identify documentation published by World Health Organization, United Nations Office on Drugs and Crime, United States Drug Enforcement Administration, and European Monitoring Centre for Drugs and Drug Addiction. Only articles or reports written in English were selected.

RESULTS

Non-fentanyl derived synthetic opioids, i.e., 2-benzylbenzimidazoles (nitazenes), brorphine, U-compounds, AH-7921, MT-45 and related compounds are characterized, describing them in terms of available forms, pharmacology, metabolism as well as their toxic effects. Sample procedures and analytical techniques available for detection and quantification of these compounds in biological matrices are also presented. Finally, as overdoses involving highly potent NSO may be difficult to reverse, the effectiveness of naloxone as a rescue agent in NSO overdose is discussed.

CONCLUSIONS

Current review presents key information on non-fentanyl derived NSO. Access to upto-date data on substances of abuse is of great importance for clinicians, public health authorities and professionals performing analyses of biological samples.

Trends in naloxone prescribed at emergency department discharge: A national analysis (2012-2019)

BACKGROUND

While having access to naloxone is recommended for patients at risk for opioid overdose, little is known about trends in national naloxone prescribing rates in emergency departments (EDs) both for co-prescription with opioids and for patients who presented with opioid abuse or overdose. This study aims to evaluate the change in naloxone prescribing and opioid/naloxone co-prescribing at discharge using national data.

METHODS

We conducted an IRB exempt retrospective review of data collected by the National Hospital Ambulatory Medical Care Survey from 2012 to 2019. The primary outcome was trend in rate of naloxone prescribing at discharge from ED visits. We also computed the proportion of visits where naloxone was both administered in the ED and prescribed at discharge, where naloxone and opioids were co-prescribed at discharge, and where an opioid was administered during the ED visit and naloxone was prescribed at discharge. All data were summarized using descriptive statistics and Spearman's Rho (SR) or Pearson's correlation (PR) were used to describe trends.

RESULTS

There was an estimated total of 250,365 patient visits where naloxone was prescribed at discharge with an increasing rate over time (0% of all ED visits in 2012 to 0.075% in 2019, p = 0.002). There were also increases in naloxone being both administered in the ED and prescribed at discharge (PC: 0.8, p = 0.02) as well as in naloxone and opioid co-prescribing (SR: 0.76, P = 0.03). There was an increase in utilization of opioids during the ED visit and naloxone prescribing at discharge for the same visit (SR: 0.80, p = 0.02).

CONCLUSION

There are increases in naloxone prescribing at discharge, naloxone and opioid co-prescribing, and opioid utilization during the same visit where naloxone is prescribed at discharge. Future studies should be done to confirm such trends, and targeted interventions should be put into place to increase access to this life-saving antidote.

Amphetamines modulate fentanyl-depressed respiration in a bidirectional manner

BACKGROUND

The opioid epidemic remains one of the most pressing public health crises facing the United States. Fentanyl and related synthetic opioid agonists have largely driven the rising rates of associated overdose deaths, in part, because of their surreptitious use as substitutes for other opioids and as adulterants in psychostimulants. Deaths involving opioids typically result from lethal respiratory depression, and it is currently unknown how co-use of psychostimulants with opioids affects respiratory toxicity. Considering psychostimulant overdoses have increased over 3-fold since 2013, and half of those co-involved opioids, this is a cardinal question.

METHODS

Naloxone, d-amphetamine (AMPH), and (±)-methamphetamine (METH) were evaluated for their effects on basal and fentanyl-depressed respiration. Minute volume (MVb) was measured in awake, freely moving mice via whole-body plethysmography to quantify fentanyl-induced respiratory depression and its modulation by dose ranges of each test drug.

RESULTS

Naloxone immediately reversed respiratory depression induced by fentanyl only at the highest dose tested (10 mg/kg). Both AMPH and METH exhibited bidirectional effects on MVb under basal conditions, producing significant (p ≤ 0.05) depressions then elevations of respiration as dose increased. Under depressed conditions the bidirectional effects of AMPH and METH on respiration were exaggerated, exacerbating and then reversing fentanyl-induced depression as dose increased.

CONCLUSIONS

These results indicate that co-use of amphetamines with fentanyl may worsen respiratory depression, but conversely, monoaminergic components of the amphetamines may possibly be exploited to mitigate fentanyl overdose.

A measurement invariance analysis of selected Opioid Overdose Knowledge Scale (OOKS) items among bystanders and first responders

The Opioid Overdose Knowledge Scale (OOKS) is widely used as an adjunct to opioid education and naloxone distribution (OEND) for assessing pre- and post-training knowledge. However, the extent to which the OOKS performs comparably for bystander and first responder groups has not been well determined. We used exploratory structural equation modeling (ESEM) to assess the measurement invariance of an OOKS item subset when used as an OEND training pre-test. We used secondary analysis of pre-test data collected from 446 first responders and 1,349 bystanders (N = 1,795) attending OEND trainings conducted by two county public health departments. Twenty-four items were selected by practitioner/trainer consensus from the original 45-item OOKS instrument with an additional 2 removed owing to low response variation. We used exploratory factor analysis (EFA) followed by ESEM to identify a factor structure, which we assessed for configural, metric, and scalar measurement invariance by participant group using the 22 dichotomous items (correct/incorrect) as factor indicators. EFA identified a 3-factor model consisting of items assessing: basic overdose risk information, signs of an overdose, and rescue procedures/advanced overdose risk information. Model fit by ESEM estimation versus confirmatory factor analysis showed the ESEM model afforded a better fit. Measurement invariance analyses indicated the 3-factor model fit the data across all levels of invariance per standard fit statistic metrics. The reduced set of 22 OOKS items appears to offer comparable measurement of pre-training knowledge on opioid overdose risks, signs of an overdose, and rescue procedures for both bystanders and first responders.

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.

Naloxone administration among opioid-involved overdose deaths in 38 United States jurisdictions in the State Unintentional Drug Overdose Reporting System, 2019

BACKGROUND

The majority of drug overdose deaths in the United States involve opioids, and synthetic opioid-involved overdose death rates are increasing. Naloxone is a key prevention strategy yet estimates of its administration are limited.

METHODS

We analyzed 2019 data from 37 states and the District of Columbia in CDC's State Unintentional Drug Overdose Reporting System to estimate the percentage of decedents, by sociodemographic subgroup, who experienced a fatal opioid-involved overdose and had no evidence of naloxone administration.

RESULTS

A total of 77.3% of 33,084 opioid-involved overdose deaths had no evidence of naloxone administration. Statistically significant subgroup differences were observed for all sociodemographic groups examined except housing status. The highest percentages of decedents lacking evidence of naloxone administration were those with highest educational attainment (doctorate or professional degree, 87.0%), oldest (55-64 years, 83.4%; ≥65 years, 87.3%) and youngest ages (<15 years, 87.5%), and single marital status (84.5%). The lowest percentages of no evidence of naloxone administration were observed for non-Hispanic American Indian/Alaskan Native persons (66.2%) and those ages 15-24 years (70.8%).

CONCLUSIONS

More than three-quarters of opioid-involved overdose deaths had no evidence of naloxone administration, underscoring the need to ensure sufficient naloxone access and capacity for utilization. While fatal overdose data cannot fully characterize sociodemographic disparities in naloxone administration, naloxone education and access efforts can be informed by apparent inequities. Public health partners can assist persons who use drugs (PWUD) by maintaining naloxone supply and amplifying messages about the high risk of using drugs alone among PWUD and their social networks.

Comparison of intranasal and intramuscular naloxone in opioid overdoses managed by ambulance staff: a double-dummy, randomised, controlled trial

AIMS

To measure and evaluate clinical response to nasal naloxone in opioid overdoses in the pre-hospital environment.

DESIGN

Randomised, controlled, double-dummy, blinded, non-inferiority trial, and conducted at two centres.

SETTING

Participants were included by ambulance staff in Oslo and Trondheim, Norway, and treated at the place where the overdose occurred.

PARTICIPANTS

Men and women age above 18 years with miosis, rate of respiration ≤8/min, and Glasgow Coma Score <12/15 were included. Informed consent was obtained through a deferred-consent procedure.

INTERVENTION AND COMPARATOR

A commercially available 1.4 mg/0.1 mL intranasal naloxone was compared with 0.8 mg/2 mL naloxone administered intramuscularly.

MEASUREMENTS

The primary end-point was restoration of spontaneous respiration of ≥10 breaths/min within 10 minutes. Secondary outcomes included time to restoration of spontaneous respiration, recurrence of overdose within 12 hours and adverse events.

FINDINGS

In total, 201 participants were analysed in the per-protocol population. Heroin was suspected in 196 cases. With 82% of the participants being men, 105 (97.2%) in the intramuscular group and 74 (79.6%) in the intranasal group returned to adequate spontaneous respiration within 10 minutes after one dose. The estimated risk difference was 17.5% (95% CI, 8.9%-26.1%) in favour of the intramuscular group. The risk of receiving additional naloxone was 19.4% (95% CI, 9.0%-29.7%) higher in the intranasal group. Adverse reactions were evenly distributed, except for drug withdrawal reactions, where the estimated risk difference was 6.8% (95% CI, 0.2%-13%) in favour of the intranasal group in a post hoc analysis.

CONCLUSION

Intranasal naloxone (1.4 mg/0.1 mL) was less efficient than 0.8 mg intramuscular naloxone for return to spontaneous breathing within 10 minutes in overdose patients in the pre-hospital environment when compared head-to-head. Intranasal naloxone at 1.4 mg/0.1 mL restored breathing in 80% of participants after one dose and had few mild adverse reactions.

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.

Treatment of opioid overdose: current approaches and recent advances

BACKGROUND

The USA has recently entered the third decade of the opioid epidemic. Opioid overdose deaths reached a new record of over 74,000 in a 12-month period ending April 2021. Naloxone is the primary opioid overdose reversal agent, but concern has been raised that naloxone is not efficacious against the pervasive illicit high potency opioids (i.e., fentanyl and fentanyl analogs).

METHODS

This narrative review provides a brief overview of naloxone, including its history and pharmacology, and the evidence regarding naloxone efficacy against fentanyl and fentanyl analogs. We also highlight current advances in overdose treatments and technologies that have been tested in humans.

RESULTS AND CONCLUSIONS

The argument that naloxone is not efficacious against fentanyl and fentanyl analogs rests on case studies, retrospective analyses of community outbreaks, pharmacokinetics, and pharmacodynamics. No well-controlled studies have been conducted to test this argument, and the current literature provides limited evidence to suggest that naloxone is ineffective against fentanyl or fentanyl analog overdose. Rather a central concern for treating fentanyl/fentanyl analog overdose is the rapidity of overdose onset and the narrow window for treatment. It is also difficult to determine if other non-opioid substances are contributing to a drug overdose, for which naloxone is not an effective treatment. Alternative pharmacological approaches that are currently being studied in humans include other opioid receptor antagonists (e.g., nalmefene), respiratory stimulants, and buprenorphine. None of these approaches target polysubstance overdose and only one novel approach (a wearable naloxone delivery device) would address the narrow treatment window.

Isolation, Identification and Structural Verification of a Methylene-Bridged Naloxone "Dimer" Formed by Formaldehyde

We report the isolation and characterization of a methylene bridged "dimer" of the opioid antagonist Naloxone, previously detected in experimental Buprenorphine-Naloxone oral films. This compound was found to form via an aldol addition followed by a condensation reaction under acidic conditions between two units of Naloxone and one unit of formaldehyde. HPLC-UV-HRMS analysis revealed the formation of three individual stereoisomers during this reaction, which were separately isolated using solid-phase extraction. These isomers were shown to freely react into one another in solvent, forming an equilibrium. The structure of the unknown compound was determined via HRMS spectrometry and 1D and 2D NMR spectroscopy.

Trends in the Utilization and Dose of Gabapentinoids in Combination With Opioids in an Injured Worker Population Between 2008 and 2018

OBJECTIVE

To determine long term (11 year) trends in gabapentin and pregabalin prescribing among workers' compensation claimants at various opioid dose combinations (low, medium, high, and very high) in Louisiana.

METHOD

A longitudinal study of 18,737 claimants who filled any prescriptions between 2008 and 2018.

RESULTS

The proportion of claimants prescribed opioids alone at all dose levels decreased dramatically. The proportion claimants prescribed the combination of low dose opioids and low dose gabapentinoids increased (7.7% to 10.9%). Prescribing higher daily doses of gabapentinoids was associated with higher daily doses of opioids. Gabapentinoid prescribing was associated with continued prescribing of medium and high dose opioids as claims matured.

CONCLUSIONS

Overall opioid prescribing decreased over time, while prescribing low dose opioids with gabapentinoids, increased.

The naloxone delivery cascade: Identifying disparities in access to naloxone among people who inject drugs in Los Angeles and San Francisco, CA

BACKGROUND

Opioid overdoses are a leading cause of injury death in the United States. Providing people who inject drugs (PWID) with naloxone is essential to preventing deaths. However, research regarding gaps in naloxone delivery is limited.

METHODS

We interviewed 536 PWID in San Francisco and Los Angeles, California from 2017 to 2018. We described naloxone engagement and re-engagement cascades, and identified factors associated with receiving naloxone in the past six months and currently owning naloxone.

RESULTS

The engagement cascade showed 72 % of PWID ever received naloxone, 49 % received it in the past six months, and 35 % currently owned naloxone. The re-engagement cascade showed, among PWID who received naloxone in the past six months, 74 % used and/or lost naloxone, and 67 % refilled naloxone. In multivariable analyses, identifying as Latinx (aRR = 0.53; 95 % CI: 0.39, 0.72) and Black (aRR = 0.73; 95 % CI: 0.57, 0.94) vs White were negatively associated with receiving naloxone in the past six months, while using opioids 1-29 times (aRR = 1.35; 95 % CI: 1.04, 1.75) and 30+ times (aRR = 1.52; 95 % CI: 1.17, 1.99) vs zero times in the past 30 days and witnessing an overdose in the past six months (aRR = 1.69; 95 % CI: 1.37, 2.08) were positively associated with receiving naloxone in the past six months. In multivariable analyses, being unhoused vs housed (aRR = 0.82; 95 % CI: 0.68, 0.99) was negatively associated with currently owning naloxone.

CONCLUSIONS

Our study adds to the literature by developing naloxone engagement and re-engagement cascades to identify disparities. Naloxone scale-up should engage populations facing inequitable access, including people of color and those experiencing homelessness.

Overdoses due to fentanyl and its analogues (F/FAs) push naloxone to the limit

WHAT IS KNOWN AND OBJECTIVE

Food and Drug Administration (FDA) risk evaluation and mitigation strategies (REMs) encourage emergency responders, paramedics, law enforcement agents, and even laypeople to be trained in the administration of naloxone with the intent of rescuing individuals from a known or suspected opioid overdose.

COMMENT

Although naloxone is generally safe and effective at reversing respiratory depression caused by a conventional opioid such as morphine or heroin by competing with the opioid and displacing it from the μ-opioid receptor, questions increasingly are arising as to whether naloxone can adequately reverse opioid overdoses that may involve the potent opioids fentanyl and its analogues (F/FAs). In other words, as more and more opioid overdoses involve F/FAs, can naloxone keep up?

WHAT IS NEW AND CONCLUSION

As a competitive antagonist at μ-opioid receptors, naloxone is often a life-saving agent in cases of overdose caused by conventional opioids, but it may not be versatile or powerful enough to combat the rising tide of overdoses due to fentanyl and its illicit analogues, or in cases of overdose involving combinations of opioids and non-opioids.

Concentrations of para-Fluorofuranylfentanyl (FFF) in Paired Central and Peripheral Blood Collected During Postmortem Death Investigations

The opioid epidemic in the United States (U.S.) has been associated with an increasing mortality rate in large part due to the emergence and proliferation of synthetic opioids over the last fifteen years. Fentanyl and its analogues have played a large part in these statistics due to their potency and toxicity. Fluorofuranylfentanyl (FFF) is a fentanyl analogue that emerged in the U.S. in 2018 and was associated with numerous adverse events and deaths. During this study, a liquid chromatography tandem mass spectrometry (LC-MS/MS) workflow was developed to accurately identify the isomer of FFF present (ortho- vs. meta- vs. para-) in medicolegal death investigation cases from Pinellas County, Florida. FFF was quantified in central and peripheral blood samples collected at autopsy. In addition, the metabolism of FFF was studied using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). para-FFF was quantitatively confirmed in 29 postmortem cases; no other isomer of FFF was detected. Central blood concentrations ranged between 0.66 and 73 ng/mL (mean = 11±14 ng/mL, median = 10 ng/mL) and peripheral blood concentrations ranged between 0.53 and 23 ng/mL (mean = 5.7±6.4 ng/mL, median = 2.7 ng/mL). Comparison of central to peripheral blood concentrations were evaluated to determine the possibility of postmortem redistribution (PMR). The metabolism of ortho-FFF was studied and found to undergo metabolic processes similar to fentanyl, producing ortho-fluorofuranyl-norfentanyl, fluoro-4-ANPP, and hydroxylated species. The results of this study demonstrate the toxicity of FFF and its implication in medicolegal death investigations. Laboratories must remain aware of new or re-emerging fentanyl analogues, as they pose significant risks to public health and public safety.

Relative addictive potential of opioid analgesic agents

Opioid overdoses and deaths continue to be a problem in the USA with a significant portion related to prescribed opioid analgesic agents. The role of pharmacogentic factors in opioid addiction is an active area of research. While all opioid analgesic agents have some addictive potential, it is clear that there are some with greater addictive potential. Oxycodone is the most widely abused opioid analgesic and it appears to predispose to chronic use with high likability by users. Fentanyl and hydromorphone are both very lipophilic allowing rapid penetration into the CNS, but are not rated as highly as other agents. Providers should consider the risk of addiction with the opioids they prescribe and give those with a lower addictive potential.

Challenges and Barriers in Applying Natural Language Processing to Medical Examiner Notes from Fatal Opioid Poisoning Cases

We detail the challenges and barriers in applying natural language processing techniques to a collection of medical examiner case investigation notes related to fatal opioid poisonings. Major advances in biomedical informatics have made natural language processing (NLP) of medical texts both a realistic and useful task. Biomedical NLP tools are typically designed to process documents originating from biomedical libraries or electronic health records (EHRs). The usefulness of biomedical NLP tools on texts authored outside of EHRs is unclear, despite an abundance of medicolegal documents existing at the intersection of medicine and law. In particular, we detail our experiences processing unstructured text and extracting semantic concepts using case investigation notes; these notes were authored by trained investigative professionals working in a medical examiner's office and describe cases containing deaths related to fatal opioid poisonings. Applying NLP to case notes is a particularly important step in generalizing the advances of biomedical NLP for other related domains and giving guidance to data scientists working with unstructured data generated outside of EHRs.

A review of performance assessment tools for rescuer response in opioid overdose simulations and training programs

Since the 1990s, more than 600 overdose response training and education programs have been implemented to train participants to respond to an opioid overdose in the United States. Given this substantial investment in overdose response training, valid assessment of a potential rescuers' proficiency in responding to an opioid overdose is important. The aim of this article is to review the current state of the literature on outcome measures utilized in opioid overdose response training. Thirty-one articles published between 2014 and 2020 met inclusion criteria. The reviewed articles targeted laypersons, healthcare providers, and first responders. The assessment tools included five validated questionnaires, fifteen non-validated questionnaires, and nine non-validated simulation-based checklists (e.g., completion of critical tasks and time to completion). Validated multiple choice knowledge assessment tools were commonly used to assess the outcomes of training programs. It is unknown how scores on these assessment tools may correlate with actual rescuer performance responding to an overdose. Seven studies reported ceiling effects most likely attributed to participants' background medical knowledge or experience. The inclusion of simulation-based outcome measures of performance, including the commission of critical errors and the time to naloxone administration, provides better insight into rescuer skill proficiency.

The rising crisis of illicit fentanyl use, overdose, and potential therapeutic strategies

Fentanyl is a powerful opioid anesthetic and analgesic, the use of which has caused an increasing public health threat in the United States and elsewhere. Fentanyl was initially approved and used for the treatment of moderate to severe pain, especially cancer pain. However, recent years have seen a growing concern that fentanyl and its analogs are widely synthesized in laboratories and adulterated with illicit supplies of heroin, cocaine, methamphetamine, and counterfeit pills, contributing to the exponential growth in the number of drug-related overdose deaths. This review summarizes the recent epidemic and evolution of illicit fentanyl use, its pharmacological mechanisms and side effects, and the potential clinical management and prevention of fentanyl-related overdoses. Because social, economic, and health problems that are related to the use of fentanyl and its analogs are growing, there is an urgent need to implement large-scale safe and effective harm reduction strategies to prevent fentanyl-related overdoses.