Detection of 30 Fentanyl Analogs by Commercial Immunoassay Kits

Fentanyl Test Strips for Harm Reduction: A Scoping Review

BACKGROUND

High potency synthetic opioids like fentanyl have continued to replace or contaminate the supply of illicit drugs in North America, with fentanyl test strips (FTSs) often used as a harm reduction tool for overdose prevention. The available evidence to support FTS for harm reduction has yet to be summarized.

METHODS

A search of PubMed, Ovid Embase, and Web of Science was conducted in March 2023. A 2-stage review was conducted to screen by title and abstract and then by full text by 2 reviewers. Data were extracted from each study using a standardized template.

RESULTS

A total of 91 articles were included, mostly from North America, predominantly reporting on FTS along with other harm reduction tools, and all conducted after 2016. No randomized controlled trials are reported. Robust evidence exists supporting the sensitivity and specificity of FTS, along with their acceptability and feasibility of use for people who use drugs and as a public health intervention. However, limited research is available on the efficacy of FTS as a harm reduction tool for behavior change, engagement in care, or overdose prevention.

CONCLUSIONS

Though FTSs are highly sensitive and specific for point of care testing, further research is needed to assess the association of FTS use with overdose prevention. Differences in FTS efficacy likely exist between people who use opioids and nonopioid drugs, with additional investigation strongly needed. As drug testing with point-of-care immunoassays is embraced for nonfentanyl contaminants such as xylazine and benzodiazepines, increased investment in examining overdose prevention is necessary.

Bibliometric evaluation of Journal of Analytical Toxicology as a scholarly publication according to the Web-of-Science citation database

Soon approaching its 50th anniversary, Journal of Analytical Toxicology (JAT) is an international scholarly publication specializing in analytical and forensic aspects of toxicology. Science Citation Index (SCI) and Journal Citation Reports (JCR), both of which are part of the Web-of-Science (WOS) database, were used to make a bibliometric evaluation of JAT articles. Between 1977 (volume 1) and 2023 (volume 47), a total of  n = 4,785 items were published in JAT; the top-ten most highly cited articles and the most prolific authors were identified. Changes in the journal impact factor (JIF) were studied between 1997 and 2022, and this metric varied from a low of 1.24 (2006) to a high of 3.36 (2020).The most recent JIF (2022) dropped to 2.5 and the corresponding 5 year JIF was 2.6. JAT's most highly cited article (590 cites) was a working group (SWGTOX) report dealing with standard practices for the validation of analytical methods in forensic toxicology laboratories. JAT published 62 articles each of which were cited over 100 times and the H-index for JAT was 89. The most prolific author of JAT articles was credited with 119 items, the first in 1980 (volume 4) and the latest in 2023 (volume 47). JAT articles were cited 4,537 times in 2022 by all journals in the JCR database, although 520 of these were self-citations (11.5%). Bibliometric methods are increasingly used to evaluate the published work of individual scientists, university departments, entire universities and whole countries. Highly cited articles are considered more influential and authoritative compared with papers that are seldom or never cited.

Testing the test strips: laboratory performance of fentanyl test strips

BACKGROUND

The overdose crisis driven by synthetic opioids continues to escalate in the USA. We evaluated the efficacy of multiple manufacturing lots of a fentanyl test strip (FTS) to detect fentanyl and fentanyl analogs and assessed cross-reactivity with possible interferences.

METHODS

Drug standards were dissolved in water in a laboratory setting and serially diluted. Drug dilutions were tested using five different manufacturing lots of BTNX Rapid Response (20 ng/mL cutoff) lateral flow chromatographic immunoassay strips to assess lot-to-lot variability for FTS sensitivity and cross-reactivity for the analytes of interest.

RESULTS

All five manufacturing lots cross-reacted with fentanyl and eleven fentanyl analogs. Diphenhydramine, lidocaine, MDMA, and methamphetamine were found to cause false positives with the strips. There was notable lot-to-lot variability in the sensitivity of the strips for fentanyl, fentanyl analogs, and known interferences.

DISCUSSION

FTS remains an important overdose prevention tool, but lot-to-lot variability in performance complicates robust instructions that balance the prevention of false positives and false negatives. Continued lot-to-lot performance assessment is recommended to ensure health education for FTS remains accurate. More sophisticated drug checking technologies and services are needed in the community landscape to augment personal FTS use to facilitate informed consumption and overdose risk mitigation.

Molecular Pharmacology Profiling of Phenylfentanil and Its Analogues to Understand the Putative Involvement of an Adrenergic Mechanism in Fentanyl-Induced Respiratory Depression

While there are approved therapeutics to treat opioid overdoses, the need for treatments to reverse overdoses due to ultrapotent fentanyls remains unmet. This may be due in part to an adrenergic mechanism of fentanyls in addition to their stereotypical mu-opioid receptor (MOR) effects. Herein, we report our efforts to further understanding of the functions these distinct mechanisms impart. Employing the known MOR neutral antagonist phenylfentanil as a lead, 17 analogues were designed based on the concept of isosteric replacement. To probe mechanisms of action, these analogues were pharmacologically evaluated in vitro and in vivo, while in silico modeling studies were also conducted on phenylfentanil. While it did not indicate MOR involvement in vivo, phenylfentanil yielded respiratory minute volumes similar to those caused by fentanyl. Taken together with molecular modeling studies, these results indicated that respiratory effects of fentanyls may also correlate to inhibition of both α1A- and α1B-adrenergic receptors.

Evaluation of portable gas chromatography-mass spectrometry (GC-MS) for the analysis of fentanyl, fentanyl analogs, and other synthetic opioids

Potent synthetic opioids including fentanyl and its analogs are frequently encountered in the field and require detection and identification by first responders to maintain the safety of drug abusers, first responders, health-care providers, and the public at large. Due to the low concentration at which these substances may be encountered and the complicating matrices within which they may be dispersed, the use of portable gas chromatography-mass spectrometry (GC-MS) for their identification in the field offers great potential value. This research established that portable GC-MS is a useful method for the detection and identification of a large number of synthetic opioids, especially fentanyl and its analogs. In this study, 250 synthetic opioids and related substances including 210 fentanyl analogs were analyzed using portable GC-MS. It was concluded that 225 of the 250 (90.0%) opioids analyzed were successfully detected onboard at the time of analysis and identified as either the substance (55.2%) or an analog (34.8%). These outcomes have equivalent benefit for the field analysis of illicit drugs due to both initiating the same subsequent actions by first responders.

Evaluating the sensitivity, stability, and cross-reactivity of commercial fentanyl immunoassay test strips

Illicit fentanyl has flooded the United States' drug market, increasing the risk of overdose and poisonings throughout the general population and accidental exposure among law enforcement officers confiscating the increasing number of seizures. Fentanyl test strips (FTS) are used to obtain presumptive information about the presence of fentanyl in a suspected sample. However, their adoption by law enforcement personnel and seized-drug analysts has been limited because most products are advertised for urine testing, not for assays using water solutions. This study presents an evaluation of four commercial FTS: Rapid Response from BTNX, Inc.; T-Dip Fentanyl (FTY) Urine Dip Cards obtained from Amazon.com; Premier BioDip FYL10 from Premier Biotech Inc.; and MobileDetect Fentanyl strips from DetectaChem, Inc. Performance characteristics curves were used to compare the products' sensitivity, showing that all can reliably detect fentanyl in aqueous solutions at concentrations below 1 μg/mL, with some of the tests able to reliably detect the drug at 200 ng/mL. A stability study demonstrates the performance of all four FTS brands was only slightly affected after 30 days of storage at two extreme environmental conditions. Fentanyl-related substances are also evaluated using the Rapid Response FTS, which showed high cross-reactivity with para-fluorofentanyl and acetylfentanyl, but lower with ortho-chlorofentanyl, carfentanil, and 4-ANPP. Users should be aware that FTS may give false-negative results even when potentially dangerous levels of carfentanil are present. When testing other common drugs, adulterants, and diluents frequently encountered in seized tablets, concentration-dependent results were obtained and multiple instances of false positives were recorded.

Evaluation of fentanyl immunoassay test strips for rapid in-situ detection of fentanyl and fentanyl analogs in seized samples and alternative matrices

BACKGROUND

Ion mobility spectrometry is used for the rapid detection of drugs at points of security but are unable to differentiate some drugs leading to the instrument alarming for a drug not present in the sample. This can be particularly problematic for samples that alarm for fentanyl. In this study, fentanyl immunoassay strips were evaluated for use as a secondary test for fentanyl, including for the testing of alternative matrices, such as powders, e-liquids, and infused papers and textiles.

METHODS

The limit of detection of fentanyl immunoassay strips was examined along with their selectivity to 18 fentanyl analogsand 72 other drugs and cutting agents. The effectiveness of the test strips at the detection of fentanyl in the presence of other drugs was examined by testing a series of concentrations of fentanyl in solution in combination with other drugs. The testing of alternative matrices was explored with laboratory prepared samples through sampling with cotton buds and extraction in water.

RESULTS

The fentanyl immunoassay strips detected fentanyl at concentrations of 45 ng/mL and reacted with 16 of 18 tested fentanyl analogs with carfentanil and norfentanyl being the only analogs to not react. There was no reactivity with other drugs or cutting agents. The effectiveness of the fentanyl test strips was not reduced when fentanyl was mixed with other drugs. Fentanyl was successfully detected with high sensitivity in all alternative matrices.

CONCLUSION

The fentanyl immunoassay strips were found to be an effective secondary test for fentanyl and at least 16 fentanyl analogs in seized drug samples, including when mixed with other drugs. The effectiveness of the sampling methods for alternative matrices should be further evaluated using fentanyl and fentanyl analog casework samples. The use of this method by law enforcement and other agencies should be examined to assess its effectiveness and ease of use in operational settings.

Advances in fentanyl testing

Fentanyl is a synthetic opioid that was approved by the FDA in the late 1960s. In the decades since, non-prescription use of fentanyl, its analogs, and structurally unrelated novel synthetic opioids (NSO) has become a worsening public health crisis. There is a clear need for accessible testing for these substances in biological specimens and in apprehended drugs. Immunoassays for fentanyl in urine are available but their performance is restricted to facilities that hold moderate complexity laboratory licenses. Immunoassays for other matrices such as oral fluid (OF), blood, and meconium have been developed but are not widely available. Point of care tests (POCT), such as lateral flow immunoassays or fentanyl test strips (FTS), are widely available but not approved by the FDA for clinical use. All immunoassays are vulnerable to false positive and false negative results. Immunoassays may or may not be able to detect fentanyl analogs and NSOs. Mass spectrometry (MS) can accurately and reliably measure fentanyl and its major metabolite norfentanyl in urine and oral fluid. MS is available at reference laboratories and large hospitals. Liquid chromatography paired with tandem mass spectrometry (LC-MS/MS) is the most widely used method and has outstanding specificity and sensitivity for fentanyl and norfentanyl. When compared to immunoassays, MS is more expensive, requires more technical skill, and takes longer to result. Newer mass spectrometry methods can measure fentanyl analogs and NSO. Both mass spectrometry assays and immunoassays [in the form of fentanyl test strips (FTS)] have potential use in harm reduction programs.

Suite of Aptamer-Based Sensors for the Detection of Fentanyl and Its Analogues

Fentanyl and its analogues are potent synthetic opioids that are commonly abused and are currently the number one cause of drug overdose death in the United States. The ability to detect fentanyl with simple, rapid, and low-cost tools is crucial for forensics, medical care, and public safety. Conventional on-site testing options for fentanyl detection─including chemical spot tests, lateral-flow immunoassays, and portable Raman spectrometers─each have their own unique flaws that limit their analytical utility. Here, we have developed a series of new aptamer-based assays and sensors that can detect fentanyl as well as several of its analogues in a reliable, accurate, rapid, and economic manner. These include colorimetric, fluorescent, and electrochemical sensors, which can detect and quantify minute quantities of fentanyl and many of its analogues with no response to other illicit drugs, cutting agents, or adulterants─even in interferent-ridden binary mixtures containing as little as 1% fentanyl. Given the high performance of these novel analytical tools, we foresee the potential for routine use by medical and law enforcement personnel as well as the general public to aid in rapid and accurate fentanyl identification.

Detection of 58 fentanyl analogs using ARK fentanyl II and Immunalysis fentanyl immunoassays

OBJECTIVES

The ability to detect fentanyl analogs in urine aids in patient management. Little is published about the new ARK™ Fentanyl II Assay formulation's ability to detect fentanyl analogs. Norfentanyl (fentanyl metabolite) cross-reactivity with the ARK II assays is 7%, while the Immunalysis SEFRIA assay norfentanyl cross-reactivity is approximately 0.005%. The purpose of this study was to determine the new ARK II and SEFRIA fentanyl assays' detection of 58 fentanyl analogs.

DESIGN & METHODS

Drug-free urine was fortified with 0-100 ng/mL (0-0.297 µmol/L) of the fentanyl analog and analyzed using the previously evaluated immunoassays. Results were compared to molecular structure. Of the 58 analogs tested at ≤ 100 ng/mL (0-0.297 µmol/L), the ARK II and SEFRIA assays produced 51 and 57 positive results respectively. The cross-reactivity of the assay was predominantly determined by the location of the modification. Most modifications to the aniline ring and/or amide group did not affect the ARK II or SEFRIA assay. Modifications to the piperidine ring decreased detection by ARK II assay. Of the 7 compounds which were undetected by the ARK II assay, all had modifications to the N-alkyl chain. Norsufentanil was not detected by either assay and was the only analog not detected by the SEFRIA assay.

CONCLUSIONS

The ARK II and Immunalysis fentanyl immunoassays can detect a range of fentanyl analogs with acryl, butyryl, or furanyl modifications to the amide group or aniline ring of the molecule. N-alkyl chain and piperidine ring modifications significantly affect the ARK II assay's ability to detect the analogs, while the SEFRIA assay appeared less affected and detected all analogs tested except for norsufentanil, which was also not detected by the ARK II assay.

High-throughput quantitative binding analysis of DNA aptamers using exonucleases

Aptamers are nucleic acid bioreceptors that have been used in various applications including medical diagnostics and as therapeutic agents. Identifying the most optimal aptamer for a particular application is very challenging. Here, we for the first time have developed a high-throughput method for accurately quantifying aptamer binding affinity, specificity, and cross-reactivity via the kinetics of aptamer digestion by exonucleases. We demonstrate the utility of this approach by isolating a set of new aptamers for fentanyl and its analogs, and then characterizing the binding properties of 655 aptamer-ligand pairs using our exonuclease digestion assay and validating the results with gold-standard methodologies. These data were used to select optimal aptamers for the development of new sensors that detect fentanyl and its analogs in different analytical contexts. Our approach dramatically accelerates the aptamer characterization process and streamlines sensor development, and if coupled with robotics, could enable high-throughput quantitative analysis of thousands of aptamer-ligand pairs.

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

•

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

•

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

•

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.

Validation of a lateral flow chromatographic immunoassay for the detection of fentanyl in drug samples

BACKGROUND

Drug overdose deaths remain the primary cause of unintentional injuries in the United States. We examined the validity of a fentanyl test strip (FTS) in detecting fentanyl and its related analogs in water-based illicit drug solutions.

METHODS

Illicit drugs obtained from law enforcement (N = 343) were tested using a lateral flow chromatographic immunoassay FTS (BTNX Rapid Response) and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) at a clinical chemistry laboratory in Baltimore, Maryland.

RESULTS

The FTS assay detected fentanyl at 200 ng/ml in water, and 13 additional fentanyl analogs, but failed to detect carfentanil and furanyl fentanyl at or below 1000 ng/ml. Overall sensitivity and specificity for detecting fentanyls was 98.5 % and 89.2 %; and the false negative and positive rate was 1.5 % and 10.9 %. False negatives (n = 2) occurred in fentanyl and a fentanyl precursor. False positives (n = 23) occurred in the presence of other illicit drugs and compounds (56.5 %) or when fentanyls were present below 40 ng/ml (43.5 %). False positive/negative rates remained low when testing cocaine and prescription opioid (PO) samples.

CONCLUSIONS

FTS is a valid drug checking tool, however, rapid immunoassays and other drug checking instruments that can detect a wider range of fentanyl analogs including carfentanil need to be prioritized to minimize accidental exposure to the full spectrum of fentanyls.

Combating illicit fentanyl: Will increased Chinese regulation generate a public health crisis in India?

This study examines how Chinese drug regulations are shifting illicit fentanyl production from China to India. This change has implications for the law, drug enforcement, pharmaceutical industry, and public health, as domestic production increases domestic access to fentanyl, in India. An empirical examination of current trends in fentanyl production and use in the region is conducted, along with an exegesis of the legal and regulatory systems in China and India. There is an accounting of the chemical and pharmaceutical industries, the strengths and weaknesses of drug legislation, and the public health consequences of increased production, distribution, and use of fentanyl in India. This study also details how the Indian government meets this challenge through legislative mechanisms, foremost through class-wide legislative control over fentanyl and its precursors. Class-wide control prohibits the unlawful production and distribution of all current and future fentanyl analogs and their precursors, disincentivizing and disrupting their development and production. The Indian government should also reduce domestic demand by promoting harm reduction measures such as opioid substitution therapy, evidence-based treatment, fentanyl test strip and naloxone distribution, and needle exchange programs.

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.

Severe poisoning after smoking a mixture of 4-fluoroisobutyryl fentanyl (4-FiBF) and alpha-pyrolidinoisohexaphenone (α-PiHP)

CONTEXT

Intoxications after ingestion of new psychoactive substances are currently one of the most challenging issues in clinical toxicology. Synthetic cathinones represented the largest group of drugs seized in 2020, but the increasing distribution of fentanyl analogues is resulting in a growing global opioid crisis. In addition, synthetic opioids may be intentionally combined with psychostimulants by drug manufacturers to reduce depressive effects. We report a case of severe poisoning after smoking a mixture of 4-fluoroisobutyryl fentanyl (4-FiBF) and alpha-pyrrolidinoisohexaphenone (α-PiHP).

CASE DETAILS

A 29-year-old male was found out of conscious in his apartment and taken to the Intensive Care Unit. Examinations revealed pinpoint pupils, slight respiratory acidosis, leukocytosis as well as body temperature of 39.4 °C and increased creatinine with decreased eGFR level. Toxicological analysis of biological samples revealed presence of 4-FiBF and α-PiHP in concentrations: 87.7 ng/mL and 5.0 ng/mL (blood) and 2291.0 ng/mL and 722.2 ng/mL (urine), respectively. After 4 days, the patient was discharged home.

DISCUSSION

Unique combination of clinical symptoms was a result of a simultaneous 4-FiBF and α-PiHP intoxication. To our knowledge, this is the first case of ingestion such unusual mixture of new psychoactive substances with a full description of medical treatment.