Validation and Cross-Reactivity Data for Fentanyl Analogs With the Immunalysis Fentanyl ELISA

Development and application of a High-Resolution mass spectrometry method for the detection of fentanyl analogs in urine and serum

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Utilization of the fentanyl analog screening kit from the Centers for Disease ControlDevelopment of a fentanyl analog high resolution mass spectrometry library.

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Fentanyl analogs are rarely identified without the co-occurrence of fentanyl.

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Fentanyl analogs fragmentation occurs at two specific bonds generating two dominate ions.

Introduction

The use of illicitly manufactured synthetic opioids, specifically fentanyl and its analogs, has escalated exponentially in the United States over the last decade. Due to the targeted nature of drug detection methods in clinical laboratories and the ever-evolving list of synthetic opioids of concern, alternative analytical approaches are needed.

Methods

Using the fentanyl analog screening (FAS) kit produced by the Centers for Disease Control and Prevention (CDC), we developed a liquid chromatography-high resolution mass spectrometry (LC-HRMS) synthetic opioid spectral library and data acquisition method using information dependent acquisition of product ion spectra. Chromatographic retention times, limits of detection and matrix effects, in urine and serum, for the synthetic opioids in the FAS kit (n = 150) were established. All urine and serum specimens sent to a clinical toxicology laboratory for comprehensive drug testing in 2019 (n = 856) and 2021 (n = 878) were analyzed with the FAS LC-HRMS library to determine the prevalence of fentanyl analogs and other synthetic opioids, retrospectively (2019) and prospectively (2021).

Results

The limit of detection (LOD) of each opioid ranged from 1 to 10 ng/mL (median, 2.5 ng/mL) in urine and 0.25–2.5 ng/mL (median, 0.5 ng/mL) in serum. Matrix effects ranged from −79 % to 86 % (median, −37 %) for urine, following dilution and direct analysis, and −80 % to 400 % (median, 0 %) for serum, following protein precipitation. The prevalence of fentanyl/fentanyl analogs in serum samples increased slightly from 2019 to 2021 while it remained the same in urine. There were only 2 samples identified that contained a fentanyl analog without the co-occurrence of fentanyl or fentanyl metabolites. Analysis of the established MS/MS spectral library revealed characteristic fragmentation patterns in most fentanyl analogs, which can be used for structure elucidation and drug identification of future analogs.

Conclusions

The LC-HRMS method was capable of detecting fentanyl analogs in routine samples sent for comprehensive drug testing. The method can be adapted to accommodate testing needs for the evolving opioid epidemic.

An Immunconjugate Vaccine Alters Distribution and Reduces the Antinociceptive, Behavioral and Physiological Effects of Fentanyl in Male and Female Rats

Fentanyl (FEN) is a potent synthetic opioid associated with increasing incidence of opioid use disorder (OUD) and fatal opioid overdose. Vaccine immunotherapy for FEN-associated disorders may be a viable therapeutic strategy. Here, we expand and confirm our previous study in mice showing immunological and antinociception efficacy of our FEN vaccine administered with the adjuvant dmLT. In this study, immunized male and female rats produced significant levels of anti-FEN antibodies that were highly effective at neutralizing FEN-induced antinociception in the tail flick assay and hot plate assays. The vaccine also decreased FEN brain levels following drug administration. Immunization blocked FEN-induced, but not morphine-induced, rate-disrupting effects on schedule-controlled responding. Vaccination prevented decreases on physiological measures (oxygen saturation, heart rate) and reduction in overall activity following FEN administration in male rats. The impact of FEN on these measures was greater in unvaccinated male rats compared to unvaccinated female rats. Cross-reactivity assays showed anti-FEN antibodies bound to FEN and sufentanil but not to morphine, methadone, buprenorphine, or oxycodone. These data support further clinical development of this vaccine to address OUD in humans.

The North American opioid epidemic: opportunities and challenges for clinical laboratories

Since 1999, the opioid epidemic in North America has resulted in over 1 million deaths, and it continues to escalate despite numerous efforts in various arenas to combat the upward trend. Clinical laboratories provide drug testing to support practices such as emergency medicine, substance use disorder treatment, and pain management; increasingly, these laboratories are collaborating in novel partnerships including drug-checking services (DCS) and multidisciplinary treatment teams. This review examines drug testing related to management of licit and illicit opioid use, new technologies and test strategies employed by clinical laboratories, barriers hindering laboratory response to the opioid epidemic, and areas for improvement and standardization within drug testing. Literature search terms included combinations of "opioid," "opiate," "fentanyl," "laboratory," "epidemic," "crisis," "mass spectrometry," "immunoassay," "drug screen," "drug test," "guidelines," plus review of PubMed "similar articles" and references within publications. While immunoassay (IA) and point-of-care (POC) test options for synthetic opioids are increasingly available, mass spectrometry (MS) platforms offer the greatest flexibility and sensitivity for detecting novel, potent opioids. Previously reserved as a second-tier application in most drug test algorithms, MS assays are gaining a larger role in initial screening for specific patients and DCS. However, there are substantial differences among laboratories in terms of updating test menus, algorithms, and technologies to meet changing clinical needs. While some clinical laboratories lack the resources and expertise to implement MS, many are also slow to adopt available IA and POC tests for newer opioids such as fentanyl. MS-based testing also presents challenges, including gaps in available guidance for assay validation and ongoing performance assessment that contribute to a dramatic lack of standardization among laboratories. We identify opportunities for improvement in laboratory operations, reporting, and interpretation of drug test results, including laboratorian and provider education and laboratory-focused guidelines. We also highlight the need for collaboration with providers, assay and instrument manufacturers, and national organizations to increase the effectiveness of clinical laboratory and provider efforts in preventing morbidity and mortality associated with opioid use and misuse.

Determination of Cross-Reactivity of Novel Psychoactive Substances with Drug Screen Immunoassays Kits in Whole Blood

The purpose of this study was to examine the impact of 59 novel psychoactive compounds on common enzyme-linked immunosorbent assay (ELISA) testing kits. Concentrations above and below the individual kit reporting limits in each class were measured. Compounds that exhibited cross-reactivity were then spiked individually using a seven-point response curve to determine the level of cross-reactivity. Diclazepam, delorazepam, phenazepam, flualprazolam, bromazolam, adinazolam, 3-methoxy-PCP, 3-hydroxy-PCP (3-OH-PCP), phenylfentanyl, para-methylacetylfentanyl and para-fluorofuranylfentanyl were determined to cross-react in the respective kits below. Herein, we detail the cross-reactivity that was observed with the above novel psychoactive substances on Immunalysis Benzodiazepine (BEN), Phencyclidine (PCP), Fentanyl (FEN), Buprenorphine (BUP), Opiates (OPI) and Oxycodone (OXY) Direct ELISA kits.

Blood concentrations of new synthetic opioids

PURPOSE

Over the last decade, there has been a significant growth in the market and number of new psychoactive substances (NPS). One of the NPS groups that has grown rapidly in recent years, bringing a new set of problems, consists of new synthetic opioids. The extreme potency of these compounds poses a high risk of acute poisoning, as an overdose can cause respiratory depression. Most of the information regarding human pharmacokinetics of new opioids is based on toxicological case reports and the data on concentrations of new opioids in human blood are scarce. The interpretation of results usually requires a comparison to previously published cases; therefore, a referenced compilation of previously published concentration data would be useful.

METHODS

The data were collected by searching the PubMed and Scopus databases and by using the Google search engine. All the available data from articles and reports that measured new opioid concentrations in plasma, serum, or whole blood were included in the data analysis.

RESULTS

The presented tables list the observed concentrations in fatal and nonfatal cases involving 37 novel synthetic opioids.

CONCLUSIONS

Blood levels of new opioids are extremely difficult to interpret. Low blood concentrations of these substances do not rule out acute poisoning as their high potency creates a risk of respiratory depression even at low doses. Opioid tolerance, frequent presence of other drugs, and additional diseases make it impossible to define concentration ranges, especially the minimum fatal concentrations. This report provides quick access to the source articles quantifying novel synthetic opioids.

Rapid quantitative determination of fentanyl in human urine and serum using a gold-based immunochromatographic strip sensor

Fentanyl is a typical opioid that is used in surgical anesthesia. However, when abused, fentanyl can lead to addiction and even death. To better control the use of fentanyl, it is necessary to develop rapid and sensitive detection methods. In this study, an ultrasensitive monoclonal antibody (mAb) was prepared and used to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and a colloidal gold-based immunochromatographic strip (CG-ICS) for the analysis of fentanyl in urine and serum. Under optimum conditions, the anti-fentanyl mAb belonging to the subtype of IgG2b showed a half-maximal inhibitory concentration (IC50) of 0.11 ng mL-1 and a linear range of detection of 0.020-0.50 ng mL-1. Fenanyl-spiked original urine and serum diluted eight times were used for the analysis of fentanyl by ic-ELISA and CG-ICS. IC50 from the standard curves was 0.46 ng mL-1 for urine and 2.6 ng mL-1 for serum in ic-ELISA and 1.6 ng mL-1 for urine and 6.27 ng mL-1 for serum in CG-ICS. The recovery test revealed that the ic-ELISA and CG-ICS, with a recovery rate of 87.0-108.4% and a coefficient of variation of 3.3-10.9%, were the same reliable tools as the liquid chromatography tandem mass spectrometry for fentanyl analysis in real samples.

High concentrations of illicit stimulants and cutting agents cause false positives on fentanyl test strips

Background

The opioid epidemic has caused an increase in overdose deaths which can be attributed to fentanyl combined with various illicit substances. Drug checking programs have been started by many harm reduction groups to provide tools for users to determine the composition of their street drugs. Immunoassay fentanyl test strips (FTS) allow users to test drugs for fentanyl by either filling a baggie or cooker with water to dissolve the sample and test. The antibody used in FTS is very selective for fentanyl at high dilutions, a characteristic of the traditional use of urine testing. These street sample preparation methods can lead to mg/mL concentrations of several potential interferents. We tested whether these concentrated samples could cause false positive results on a FTS.

Methods

20 ng/mL Rapid Response FTS were obtained from BTNX Inc. and tested against 4 different pharmaceuticals (diphenhydramine, alprazolam, gabapentin, and naloxone buprenorphine) and 3 illicit stimulants [cocaine HCl, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA)] in concentrations from 20 to 0.2 mg/mL. The FTS testing pad is divided into 2 sections: the control area and the test area. Control and test area signal intensities were quantified by ImageJ from photographs of the test strips and compared to a threshold set by fentanyl at the FTS limit of detection.

Results

False positive results indicating the presence of fentanyl were obtained from samples of methamphetamine, MDMA, and diphenhydramine at concentrations at or above 1 mg/mL. Diphenhydramine is a common cutting agent in heroin. The street sample preparation protocols for FTS use suggested by many online resources would produce such concentrations of these materials. Street samples need to be diluted more significantly to avoid interference from potential cutting agents and stimulants.

Conclusions

Fentanyl test strips are commercially available, successful at detecting fentanyl to the specified limit of detection and can be a valuable tool for harm reduction efforts. Users should be aware that when drugs and adulterants are in high concentrations, FTS can give a false positive result.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12954-021-00478-4.

Detection of 30 Fentanyl Analogs by Commercial Immunoassay Kits

Health-care workers, laboratorians and overdose prevention centers rely on commercial immunoassays to detect the presence of fentanyl; however, the cross-reactivity of fentanyl analogs with these kits is largely unknown. To address this, we conducted a pilot study evaluating the detection of 30 fentanyl analogs and metabolites by 19 commercially available kits (9 lateral flow assays, 7 heterogeneous immunoassays and 3 homogenous immunoassays). The analogs selected for analysis were compiled from the Drug Enforcement Administration and National Forensic Laboratory Information System reports from 2015 to 2018. In general, the immunoassays tested were able to detect their intended fentanyl analog and some closely related analogs, but more structurally diverse analogs, including 4-methoxy-butyryl fentanyl and 3-methylfentanyl, were not well detected. Carfentanil was only detected by kits specifically designed for its recognition. In general, analogs with group additions to the piperidine, or bulky rings or long alkyl chain modifications in the N-aryl or alkyl amide regions, were poorly detected compared to other types of modifications. This preliminary information is useful for screening diagnostic, forensic and unknown powder samples for the presence of fentanyl analogs and guiding future testing improvements.

Determination of Fentanyl, Alpha-Methylfentanyl, Beta-Hydroxyfentanyl, and the Metabolite Norfentanyl in Rat Urine by LC-MS/MS

Fentanyl and its analogs are potent synthetic opioids with a high potential for abuse and dependence. They have become major contributors to opioid deaths. This study aimed to determine whether the metabolites of fentanyl, alpha-methylfentanyl and beta-hydroxyfentanyl, excreted in the urine, can demonstrate historical drug exposure. Fentanyl is primarily metabolized via CYP3A4 into norfentanyl, although there is little research on its metabolism into alpha-methylfentanyl and beta-hydroxyfentanyl. We conducted in vitro experiments with human liver microsomes (HLM) and rat liver microsomes (RLM) to elucidate the major metabolic pathways of alpha-methylfentanyl and beta-hydroxyfentanyl using UHPLC coupled with mass spectrometry. The results showed that both alpha-methylfentanyl and beta-hydroxyfentanyl were predominantly metabolized into norfentanyl in HLM and RLM. Urine samples were collected at different intervals from 0 h to 72 h after intravenous administration of alpha-methylfentanyl and beta-hydroxyfentanyl (20 μg/kg) to Sprague-Dawley rats. We prepared the samples by liquid-liquid extraction, and the internal standard (IS) was cariprazine. A sensitive, rapid LC-MS/MS method was developed and validated to determine four analytes in the urine. The lower limit of qualification (LLOQ) in urine was 2 pg/ml for fentanyl, 5 pg/ml for alpha-methylfentanyl, 10 pg/ml for beta-hydroxyfentanyl, and 40 pg/ml for norfentanyl. The analytical range was 0.002-2 ng/ml for fentanyl, 0.005-5 ng/ml for alpha-methylfentanyl, 0.01-10 ng/ml for beta-hydroxyfentany and 0.04-40 ng/ml for norfentanyl. All analytes demonstrated good linearity (R2 > 0.99). The extraction recoveries were in the 67.8%-92.1% range, and the IS-normalized matrix effects were between 55.5%-74.0% (CV < 15%). Our data indicated that norfentanyl has a higher concentration in rat urine and was detectable for at least three days after exposure to these compounds. This developed method may be useful in various fields, including forensic analysis, workplace drug testing, and monitoring drug abuse.

Structure Elucidation of Urinary Metabolites of Fentanyl and Five Fentanyl Analogs using LC-QTOF-MS, Hepatocyte Incubations and Synthesized Reference Standards

Fentanyl analogs constitute a particularly dangerous group of new psychoactive compounds responsible for many deaths around the world. Little is known about their metabolism, and studies utilizing liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOF-MS) analysis of hepatocyte incubations and/or authentic urine samples do not allow for determination of the exact metabolite structures, especially when it comes to hydroxylated metabolites. In this study, seven motifs (2-, 3-, 4- and β-OH as well as 3,4-diOH, 4-OH-3-OMe and 3-OH-4-OMe) of fentanyl and five fentanyl analogs, acetylfentanyl, acrylfentanyl, cyclopropylfentanyl, isobutyrylfentanyl and 4F-isobutyrylfentanyl were synthesized. The reference standards were analyzed by LC–QTOF-MS, which enabled identification of the major metabolites formed in hepatocyte incubations of the studied fentanyls. By comparison with our previous data sets, major urinary metabolites could tentatively be identified. For all analogs, β-OH, 4-OH and 4-OH-3-OMe were identified after hepatocyte incubation. β-OH was the major hydroxylated metabolite for all studied fentanyls, except for acetylfentanyl where 4-OH was more abundant. However, the ratio 4-OH/β-OH was higher in urine samples than in hepatocyte incubations for all studied fentanyls. Also, 3-OH-4-OMe was not detected in any hepatocyte samples, indicating a clear preference for the 4-OH-3-OMe, which was also found to be more abundant in urine compared to hepatocytes. The patterns appear to be consistent across all studied fentanyls and could serve as a starting point in the development of methods and synthesis of reference standards of novel fentanyl analogs where nothing is known about the metabolism.

Impact of the Opioid Epidemic on Drug Testing

BACKGROUND

This review provides a description of how the opioid epidemic has impacted drug testing.

METHODS

Four major service areas of drug testing were considered, including emergency response, routine clinical care, routine forensics, and death investigations.

RESULTS

Several factors that the opioid epidemic has impacted in drug testing are discussed, including specimens, breadth of compounds recommended for testing, time to result required for specific applications, analytical approaches, interpretive support requirements, and examples of published practice guidelines.

CONCLUSIONS

Both clinical and forensic laboratories have adapted practices and developed new testing approaches to respond to the opioid epidemic. Such changes are likely to continue evolving in parallel with changes in both prescription and nonprescription opioid availability and use patterns, as well as emerging populations that are affected by the "waves" of the opioid epidemic.

Interpol review of controlled substances 2016-2019

This review paper covers the forensic-relevant literature in controlled substances from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Interpol review of toxicology 2016-2019

This review paper covers the forensic-relevant literature in toxicology from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20.Papers%202019.pdf.

Comparison of Two Commercially Available Fentanyl Screening Immunoassays for Clinical Use

BACKGROUND

Fentanyl is a synthetic opioid associated with illicit drug use and overdose deaths. The SEFRIA Immunalysis (IAL) and ARK fentanyl assays are both FDA-cleared, open channel immunoassays for fentanyl detection in urine. However, limited data are available in the literature comparing these assays. The objective of this study was to perform a direct comparison of these two fentanyl immunoassays.

METHODS

IAL and ARK fentanyl immunoassays were performed on a Roche Cobas e602 automated chemistry analyzer. Repeatability and total imprecision were compared by diluting fentanyl into urine at concentrations above, below, and at the manufacturers' cutoffs of 1.0 ng/mL. Cross-reactivity was assessed for norfentanyl and the fentanyl analogs acetylfentanyl, acrylfentanyl, and furanylfentanyl. Concordance was assessed in 90 patient samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the gold standard.

RESULTS

Repeatability varied from 11.4%-17.8% on the IAL assay and 2.8%-5.5% on the ARK assay. Total imprecision was 18.9%-40.7% on the IAL assay and 2.9%-6.4% on the ARK assay. Both assays cross-reacted with acetylfentanyl (∼100%), acrylfentanyl (∼100%), and furanylfentanyl (∼20%), but only the ARK assay cross-reacted with norfentanyl (∼3%). An admixture of 0.5 ng/mL fentanyl and 6 ng/mL norfentanyl produced a positive result on the ARK assay. Total concordance between IAL and ARK for 90 tested patient samples was 93% (kappa = 0.85). Relative to LC-MS/MS, the IAL assay had a concordance of 90% (kappa = 0.79) and the ARK assay had a concordance of 94% (kappa = 0.88). Including norfentanyl in the LC-MS/MS confirmation increased the concordance of the ARK to 96% (kappa = 0.90).

CONCLUSIONS

The ARK assay recognized the metabolite norfentanyl, demonstrated superior precision, and had better concordance with LC-MS/MS compared to the IAL assay.

LC-MS-MS vs ELISA: Validation of a Comprehensive Urine Toxicology Screen by LC-MS-MS and a Comparison of 100 Forensic Specimens

Toxicology laboratories commonly employ immunoassay methodologies to perform an initial drug screen on urine specimens to direct confirmatory testing. Due to limitations of immunoassay testing and the need to screen for a broader range of drugs with lower limits of detection at a lower cost, mass spectrometry screening techniques have gained favor in the toxicology field. A liquid chromatography-tandem mass spectrometry (LC-MS-MS) urine screening panel was developed and validated for 52 drugs and metabolites. A simple dilute-and-shoot with enzymatic hydrolysis technique was utilized to prepare the urine specimens for analysis. Limit of detection, interference, ionization suppression/enhancement, carryover and stability of processed specimens were assessed during validation. To evaluate the toxicological results obtained from utilizing the LC-MS-MS in comparison with the laboratory's current enzyme-linked immunosorbent assay (ELISA) panel, 100 authentic urine specimens from suspected driving under the influence and drug-facilitated crime cases were analyzed using both methodologies and the results were compared. In addition, the cost of each methodology was evaluated and compared. The validated LC-MS-MS method had limits of detection that were equal to or lower than the concentrations validated for ELISA cutoffs, had fewer exogenous interferences, and the cost of screening per specimen was reduced by ~70% when compared to ELISA. Comparing the toxicology results of forensic urine specimens demonstrated that by only using ELISA, the laboratory was unable to detect benzoylecgonine in 26%, lorazepam in 33% and oxymorphone in 60% of the positive specimens. Additional analytes detected using the LC-MS-MS method were zolpidem and/or metabolite, gabapentin, tramadol and metabolite, methadone and metabolite, meprobamate and phentermine. The results of the validation, the toxicological result comparison and the cost comparison showed that the LC-MS-MS screening method is a simple, sensitive and cost-effective alternative to ELISA screening methods for urine specimens.

Application of the fentanyl analog screening kit toward the identification of emerging synthetic opioids in human plasma and urine by LC-QTOF

Human exposures to fentanyl analogs, which significantly contribute to the ongoing U.S. opioid overdose epidemic, can be confirmed through the analysis of clinical samples. Our laboratory has developed and evaluated a qualitative approach coupling liquid chromatography and quadrupole time-of-flight mass spectrometry (LC-QTOF) to address novel fentanyl analogs and related compounds using untargeted, data-dependent acquisition. Compound identification was accomplished by searching against a locally-established mass spectral library of 174 fentanyl analogs and metabolites. Currently, our library can identify 150 fentanyl-related compounds from the Fentanyl Analog Screening (FAS) Kit), plus an additional 25 fentanyl-related compounds from individual purchases. Plasma and urine samples fortified with fentanyl-related compounds were assessed to confirm the capabilities and intended use of this LC-QTOF method. For fentanyl, 8 fentanyl-related compounds and naloxone, lower reportable limits (LRL₁₀₀), defined as the lowest concentration with 100 % true positive rate (n = 12) within clinical samples, were evaluated and range from 0.5 ng/mL to 5.0 ng/mL for urine and 0.25 ng/mL to 2.5 ng/mL in plasma. The application of this high resolution mass spectrometry (HRMS) method enables the real-time detection of known and emerging synthetic opioids present in clinical samples.