Bioanalytical methods for the determination of cocaine and metabolites in human biological samples

Discriminating cocaine use from other sympathomimetics using wearable electrocardiographic (ECG) sensors

BACKGROUND

Our group has established the feasibility of using on-body electrocardiographic (ECG) sensors to detect cocaine use in the human laboratory. The purpose of the current study was to test whether ECG sensors and features are capable of discriminating cocaine use from other non-cocaine sympathomimetics.

METHODS

Eleven subjects with cocaine use disorder wore the Zephyr BioHarness™ 3 chest band under six experimental (drug and non-drug) conditions, including 1) laboratory, intravenous cocaine self-administration, 2) after a single oral dose of methylphenidate, 3) during aerobic exercise, 4) during tobacco use (N=7 who smoked tobacco), and 5) during routine activities of daily inpatient living (unit activity). Three ECG-derived feature sets served as primary outcome measures, including 1) the RR interval (i.e., heart rate), 2) a group of ECG interval proxies (i.e., PR, QS, QT and QTc intervals), and 3) the full ECG waveform. Discriminatory power between cocaine and non-cocaine conditions for each of the three outcomes measures was expressed as the area under the receiver operating characteristics (AUROC) curve.

RESULTS

All three outcomes successfully discriminated cocaine use from unit activity, exercise, tobacco, and methylphenidate conditions with a mean AUROC values ranging from 0.66 to 0.99 and with least squares means values all statistically different/higher than 0.5 among all subjects [F(3, 99) = 3.38, p =0.02] and among those with tobacco use [F(4, 84) = 5.39, p = 0.0007].

CONCLUSIONS

These preliminary results support discriminatory power of wearable ECG sensors for detecting cocaine use.

Stability of Cocaine, Opiates, and Metabolites in Dried Saliva Spots

Drug abuse still represents a global problem, and it is associated with an increased risk of diseases, injuries, and deaths. Cocaine (COC) and opiates are the most abused drugs and account for a significant number of fatalities. Therefore, it is important to develop methods capable of effectively identifying and quantifying these substances. The present study aims to evaluate the long-term stability of COC, ecgonine methylester (EME), benzoylecgonine (BEG), cocaethylene (COET), norcocaine (NCOC), morphine (MOR), codeine (COD) and 6-monoacetylmorphine (6-MAM) in oral fluid samples. The analytes of interest were isolated from the matrix (50 µL) using the dried saliva spots (DSS) sampling approach and were subsequently analyzed by gas chromatography coupled with tandem mass spectrometry (GC–MS/MS). The parameters that could influence the stability of the target compounds were studied, and these were storage temperature, light, use of preservatives (and respective concentrations), and time. The effects of each parameter were evaluated using the design of experiments (DOE) approach. The stability of the target analytes was improved when the DSS were stored at room temperature, in the presence of light and using 1% sodium fluoride. The best conditions were then adopted for the DSS storage and long-term stability was assessed. COD was only stable for 1 day, EME was stable for 3 days, COC, COET, NCOC and 6-MAM were stable for 7 days, MOR for 14 days and BEG remained stable throughout the study (136 days). This is the first study that evaluates the stability of these compounds in oral fluid samples after application in DSS cards, and optimizes the conditions in order to improve their stability.

Evaluation of Cocaine Effect on Endogenous Metabolites of HepG2 Cells Using Targeted Metabolomics

Cocaine toxicity has been a subject of study because cocaine is one of the most common and potent drugs of abuse. In the current study the effect of cocaine on human liver cancer cell line (HepG2) was assessed. Cocaine toxicity (IC50) on HepG2 cells was experimentally calculated using an XTT assay at 2.428 mM. The metabolic profile of HepG2 cells was further evaluated to investigate the cytotoxic activity of cocaine at 2 mM at three different time points. Cell medium and intracellular material samples were analyzed with a validated HILIC-MS/MS method for targeted metabolomics on an ACQUITY Amide column in gradient mode with detection on a triple quadrupole mass spectrometer in multiple reaction monitoring. About 106 hydrophilic metabolites from different metabolic pathways were monitored. Multivariate analysis clearly separated the studied groups (cocaine-treated and control samples) and revealed potential biomarkers in the extracellular and intracellular samples. A predominant effect of cocaine administration on alanine, aspartate, and glutamate metabolic pathway was observed. Moreover, taurine and hypotaurine metabolism were found to be affected in cocaine-treated cells. Targeted metabolomics managed to reveal metabolic changes upon cocaine administration, however deciphering the exact cocaine cytotoxic mechanism is still challenging.

New miniaturized clean-up procedure for hair samples by means of microextraction by packed sorbent: determination of cocaine and metabolites

Cocaine is still one of the most commonly used illicit substances worldwide, with an estimated 4 million users in Europe in the last year. Hair samples have been widely used for the determination of episodic or repeated consumption of this substance, but the use of miniaturized techniques for hair sample clean-up has been challenging due to the sample complexity. Despite hair's complex matrix, MEPS provides a method that is fast, reduces the volume of extraction solvents used, and offers low-cost options (since extraction beds may be reused several times). Microextraction by packed sorbent using a mixed-mode sorbent was optimized for hair sample clean-up in order to determine cocaine, benzoylecgonine, ecgonine methyl ester, norcocaine, cocaethylene and anhydroecgonine methyl ester by gas chromatography coupled to tandem mass spectrometry. The method was fully validated according to internationally accepted criteria, presenting good linearity between the limits of quantification (0.01-0.15) and 5 ng/mg. Precision and accuracy resulted in coefficients of variation typically lower than 15%, with mean relative errors within ±15% for all compounds, except for the limit of quantification (±20%). The present work describes the first application of microextraction by packed sorbent for the concentration of cocaine and metabolites extracted from hair samples. Graphical abstract.

Blood and Plasma Volumetric Absorptive Microsampling (VAMS) Coupled to LC-MS/MS for the Forensic Assessment of Cocaine Consumption

Reliable, feasible analytical methods are needed for forensic and anti-doping testing of cocaine and its most important metabolites, benzoylecgonine, ecgonine methyl ester, and cocaethylene (the active metabolite formed in the presence of ethanol). An innovative workflow is presented here, using minute amounts of dried blood or plasma obtained by volumetric absorptive microsampling (VAMS), followed by miniaturized pretreatment by dispersive pipette extraction (DPX) and LC-MS/MS analysis. After sampling 20 µL of blood or plasma with a VAMS device, the sample was dried, extracted, and loaded onto a DPX tip. The DPX pretreatment lasted less than one minute and after elution with methanol the sample was directly injected into the LC-MS/MS system. The chromatographic analysis was carried out on a C8 column, using a mobile phase containing aqueous formic acid and acetonitrile. Good extraction yield (> 85%), precision (relative standard deviation, RSD < 6.0%) and matrix effect (< 12%) values were obtained. Analyte stability was outstanding (recovery > 85% after 2 months at room temperature). The method was successfully applied to real blood and plasma VAMS, with results in very good agreement with those of fluid samples. The method seems suitable for the monitoring of concomitant cocaine and ethanol use by means of plasma or blood VAMS testing.

Forensic Drug Profile: Cocaethylene

This article is intended as a brief review or primer about cocaethylene (CE), a pharmacologically active substance formed in the body when a person co-ingests ethanol and cocaine. Reference books widely used in forensic toxicology contain scant information about CE, even though this cocaine metabolite is commonly encountered in routine casework. CE and cocaine are equi-effective at blocking the reuptake of dopamine at receptor sites, thus reinforcing the stimulant effects of the neurotransmitter. In some animal species, the LD50 of CE was lower than for cocaine. CE is also considered more toxic to the heart and liver compared with the parent drug cocaine. The plasma elimination half-life of CE is ~2 h compared with ~1 h for cocaine. The concentrations of CE in blood after drinking alcohol and taking cocaine are difficult to predict and will depend on the timing of administration and the amounts of the two precursor drugs ingested. After an acute single dose of cocaine and ethanol, the concentration–time profile of CE runs on a lower level to that of cocaine, although CE is detectable in blood for several hours longer. A strong case can be made for adding together the concentrations of cocaine and CE in forensic blood samples when toxicological results are interpreted in relation to acute intoxication and the risk of an overdose death.

Molecular gated nanoporous anodic alumina for the detection of cocaine

We present herein the use of nanoporous anodic alumina (NAA) as a suitable support to implement "molecular gates" for sensing applications. In our design, a NAA support is loaded with a fluorescent reporter (rhodamine B) and functionalized with a short single-stranded DNA. Then pores are blocked by the subsequent hybridisation of a specific cocaine aptamer. The response of the gated material was studied in aqueous solution. In a typical experiment, the support was immersed in hybridisation buffer solution in the absence or presence of cocaine. At certain times, the release of rhodamine B from pore voids was measured by fluorescence spectroscopy. The capped NAA support showed poor cargo delivery, but presence of cocaine in the solution selectively induced rhodamine B release. By this simple procedure a limit of detection as low as 5 × 10-7 M was calculated for cocaine. The gated NAA was successfully applied to detect cocaine in saliva samples and the possible re-use of the nanostructures was assessed. Based on these results, we believe that NAA could be a suitable support to prepare optical gated probes with a synergic combination of the favourable features of selected gated sensing systems and NAA.

Assessing cocaine abuse using LC-MS/MS measurements in biological specimens

Cocaine use is still a problem in today's world, and this has several implications on human activities. Indeed, important problems related to cocaine derive from its use in situations where concentration and focus skills are necessary, namely while driving and/or working. The need of analytical methods for drug analysis in specimens of biological origin for proper documentation of human exposure is increasing. While GC-MS-based procedures represented the state-of-the-art of analytical techniques a few years ago, there is a growing trend for their replacement by LC-MS/MS, which can be justified by the increased sensitivity presented by these new technologies. This paper will review recently published papers on the use of LC-MS/MS-based procedures for cocaine measurement in biological specimens.

Validation of a fast UPLC–MS/MS method for quantitative analysis of opioids, cocaine, amphetamines (and their derivatives) in human whole blood

Background: Conventional methods for analysis of drugs of abuse require multiple assays which can be both expensive and time-consuming. This work describes a novel, rapid, simple and sensitive method for the quantification of 14 illicit drugs and their metabolites in whole blood. Results/methodology: This method employed a rapid liquid–liquid sample extraction of whole blood followed by UPLC–MS/MS analysis. Calibration curves were validated for analysis of appropriate concentrations. Inter- and intra-assay variations were <14.8%. Deviation of accuracy was <14.9% from target concentration for each quality control level. Conclusion: This work described the development and the full validation of a precise, sensitive and accurate assay. After validation, this new assay was successfully applied to routine toxicological analysis.

Recent trends in analytical methods and separation techniques for drugs of abuse in hair

Hair analysis of drugs of abuse has been a subject of growing interest from a clinical, social and forensic perspective for years because of the broad time detection window after intake in comparison to urine and blood analysis. Over the last few years, hair analysis has gained increasing attention and recognition for the retrospective investigation of drug abuse in a wide variety of contexts, shown by the large number of applications developed. This review aims to provide an overview of the state of the art and the latest trends used in the literature from 2005 to the present in the analysis of drugs of abuse in hair, with a special focus on separation analytical techniques and their hyphenation with mass spectrometry detection. The most recently introduced sample preparation techniques are also addressed in this paper. The main strengths and weaknesses of all of these approaches are critically discussed by means of relevant applications.

Hair as an alternative matrix in bioanalysis

Alternative matrices are steadily gaining recognition as biological samples for toxicological analyses. Hair presents many advantages over traditional matrices, such as urine and blood, since it provides retrospective information regarding drug exposure, can distinguish between chronic and acute or recent drug use by segmental analysis, is easy to obtain, and has considerable stability for long periods of time. For this reason, it has been employed in a wide variety of contexts, namely to evaluate workplace drug exposure, drug-facilitated sexual assault, pre-natal drug exposure, anti-doping control, pharmacological monitoring and alcohol abuse. In this article, issues concerning hair structure, collection, storage and analysis are reviewed. The mechanisms of drug incorporation into hair are briefly discussed. Analytical techniques for simultaneous drug quantification in hair are addressed. Finally, representative examples of drug quantification using hair are summarized, emphasizing its potentialities and limitations as an alternative biological matrix for toxicological analyses.

Determination of cocaine and its major metabolite benzoylecgonine in several matrices obtained from deceased individuals with presumed drug consumption prior to death

In the field of forensic toxicology, femoral blood is the most useful sample for the determination and quantification of drugs; however, cases in which blood is unavailable are common. In such cases, validated methodologies for drug determination in alternative matrices can be decisive in the investigation of a case. In particular, when femoral blood is unavailable for analysis for the presence of systemic exposure to cocaine and its principal metabolite, benzoylecgonine, validated methodologies from matrices other than blood that can be obtained in the autopsy room would be useful to the forensic toxicologist in the evaluation of a specific forensic case. To address this issue, we implemented and compared in our study the systematic evaluation of extraction, chromatographic separation, and quantification of cocaine and benzoylecgonine in different biological matrices (right and left cardiac blood, femoral arterial and venous blood, urine, vitreous humor, cerebrospinal fluid, brain accumbens nucleus, brain ventral tegmental area, and liver). The studied matrices were those most likely to be obtained from different autopsy rooms at the time of forensic testing in deceased individuals who are presumed of antemortem drug consumption. Solid phase extraction of analytes from the different matrices was performed using C-8/SCX mixed-phase columns, and gas chromatographic mass spectrometry separation was performed using detection in single-ion monitoring mode. The methodological validation was performed for all the studied matrices, and the results showed similar sensitivity and recoveries without statistical differences between the studied matrices. The methods were applied to evaluate a thanatological case using all the study matrices, showing unequal postmortem distribution of cocaine and benzoylecgonine throughout the different matrices tested. The present work opens the option of applying appropriate methodologies in the analysis of matrices, other than the usual blood, to obtain reliable results that may help clarify a forensic case. In addition, we present findings from different studies. This work affirms not only the potentiality of obtaining reliable data but also reaffirms the challenge of applying these data and taking into account the complexity of interpreting results in matrices other than blood.

Hair analysis following chronic smoked-drugs-of-abuse exposure in adults and their toddler: a case report

Introduction

Over the past two decades, the study of chronic cocaine and crack cocaine exposure in the pediatric population has been focused on the potential adverse effects, especially in the prenatal period and early childhood. Non-invasive biological matrices have become an essential tool for the assessment of a long-term history of drug of abuse exposure.

Case report

We analyze the significance of different biomarker values in hair after chronic crack exposure in a two-year-old Caucasian girl and her parents, who are self-reported crack smokers. The level of benzoylecgonine, the principal metabolite of cocaine, was determined in segmented hair samples (0 cm to 3 cm from the scalp, and > 3 cm from the scalp) following washing to exclude external contamination. Benzoylecgonine was detectable in high concentrations in the child's hair, at 1.9 ng/mg and 7.04 ng/mg, respectively. Benzoylecgonine was also present in the maternal and paternal hair samples at 7.88 ng/mg and 6.39 ng/mg, and 13.06 ng/mg and 12.97 ng/mg, respectively.

Conclusion

Based on the data from this case and from previously published poisoning cases, as well as on the experience of our research group, we conclude that, using similar matrices for the study of chronic drug exposure, children present with a higher cocaine concentration in hair and they experience more serious deleterious acute effects, probably due to a different and slower cocaine metabolism. Consequently, children must be not exposed to secondhand crack smoke under any circumstance.

Bioanalytical procedures and recent developments in the determination of opiates/opioids in human biological samples

The use and abuse of illegal drugs affects all modern societies, and therefore the assessment of drug exposure is an important task that needs to be accomplished. For this reason, the reliable determination of these drugs and their metabolites in biological specimens is an issue of utmost relevance for both clinical and forensic toxicology laboratories in their fields of expertise, including in utero drug exposure, driving under the influence of drugs and drug use in workplace scenarios. Most of the confirmatory analyses for abused drugs in biological samples are performed by gas chromatographic-mass spectrometric methods, but use of the more recent and sensitive liquid chromatography-(tandem) mass spectrometry technology is increasing dramatically. This article reviews recently published articles that describe procedures for the detection of opiates in the most commonly used human biological matrices, blood and urine, and also in unconventional ones, e.g. oral fluid, hair, and meconium. Special attention will be paid to sample preparation and chromatographic analysis.