Concentrations of cocaine and benzoylecgonine in femoral blood from cocaine-related deaths compared with venous blood from impaired drivers

A two-year review of cocaine findings in impaired driving investigations in Ontario, Canada

Drug-impaired driving is an increasing public safety concern across Canada, particularly due to the demonstrated increase in use of recreational drugs such as cocaine. Cocaine is a central nervous system stimulant drug; however, it can impair an individual's driving ability in both the stimulant and crash phases. Despite the scientific consensus regarding cocaine's potential for driving impairment, there is relatively little information available regarding blood concentrations and associated observations of impairment in suspected impaired drivers. Retrospective data analysis was performed to evaluate suspected impaired driving cases in which cocaine and/or benzoylecgonine were detected alone, or in combination with other drugs, in blood and urine samples submitted to the Toxicology Section of the Centre of Forensic Sciences with incident dates between 2021 and 2022. Cocaine and/or benzoylecgonine were detected in 46% (blood) and 66% (urine) of the total impaired driving samples submitted. In 41 cases where cocaine and/or benzoylecgonine were the only drug finding in blood, concentrations of cocaine and benzoylecgonine ranged from 0.0073 to 0.26 mg/L (mean 0.096 mg/L) and 0.13 to 5.3 mg/L (mean 2.1 mg/L), respectively. Driving observations reported by the arresting officer in cases where cocaine and/or benzoylecgonine were the only drug finding in blood and urine included the driver being involved in a collision, the vehicle leaving the roadway, erratic driving and the driver being asleep at the wheel; observations of drug impairment reported by the drug recognition expert at the time of driver evaluation included abnormal speech patterns, poor balance/incoordination, abnormal body movements and the individual falling asleep. The results provide concentrations of cocaine and benzoylecgonine observed in suspected impaired drivers, insight into observations that may be associated with prior cocaine use and additional information to inform on the effects of cocaine on driving.

Development of an innovative analytical method for forensic detection of cocaine, antidepressants, and metabolites in postmortem blood using magnetic nanoparticles

Cocaine and antidepressants rank high globally in substance consumption, emphasizing their impact on public health. The determination of these compounds and related substances in biological samples is crucial for forensic toxicology. This study focused on developing an innovative analytical method for the determination of cocaine, antidepressants, and their related metabolites in postmortem blood samples, using unmodified commercial Fe3O4 nanoparticles as a sorbent for dispersive magnetic solid-phase extraction (m-d-SPE), coupled with liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. An aliquot of 100 µL of whole blood and 5 µL of the internal standard pool were added to 30 mg of nanoparticles. The nanoparticles were separated from the sample using a neodymium magnet inserted into a 3D-printed microtube rack. The liquid was then discarded, followed by desorption with 300 µL of 1/1/1 acetonitrile/methanol/ethyl acetate. The sample was vortexed and separated, and 1.5 µL of the organic supernatant was injected into the LC-MS/MS. The method was acceptably validated and successfully applied to 263 postmortem blood samples. All samples evaluated in this study were positive for at least one substance. The most frequent analyte was benzoylecgonine, followed by cocaine and cocaethylene. The most common antidepressants encountered in the analyzed samples were citalopram and fluoxetine, followed by fluoxetine's metabolite norfluoxetine. This study describes the first report of this sorbent in postmortem blood analysis, demonstrating satisfactory results for linearity, precision, accuracy, and selectivity for all compounds. The method's applicability was confirmed, establishing it as an efficient and sustainable alternative to traditional techniques for forensic casework.

Post-mortem toxicological analysis of cocaine: main biological samples and analytical methods

This scoping review intends to identify the most used analytical methods and biological samples in the post-mortem forensic toxicological analysis of cocaine and its metabolites. A scoping review was performed based on the question "What are the analytical methods and types of biological samples most frequently used to identify and quantify cocaine in post-mortem forensic toxicology?" The studies were selected from five databases and, after exclusions, the data were tabulated, analyzed, and reported. Twenty-one articles published between 2012 and 2022 were filtered from five different databases to be studied. The collected data indicate that the most used biological samples were blood and hair. The most used sample preparation technique was solid phase extraction, while the most mentioned chromatography method was liquid chromatography with mass spectrometry. This review presents and discusses the state of the art regarding methods for the detection sensitivity spectrum, why limits of quantification are so important for these methods, and what are the most suitable biological samples to be utilized in each case. Cocaine and metabolites are important in forensic toxicologic post-mortem analysis. However, there is little concern in the development of miniaturized and automated sample preparation in this field. Besides, there is not enough understanding of post-mortem redistribution, tolerance, drug-drug interactions, and pre-existing medical conditions.

Postmortem redistribution of cocaine and its metabolites, benzoylecgonine and ecgonine methyl ester in humans: Important variables that might be influencing the central blood / peripheral blood ratio

INTRODUCTION

A big challenge in forensic toxicology is the correct interpretation of the results of quantitative analyses in postmortem cases. Postmortem drug concentrations not necessarily reflect the drug concentrations at the time of death, due to postmortem changes in drug concentrations caused by postmortem redistribution (PMR). Cardiac blood is more prone to PMR related concentration changes than peripheral blood. Because of this difference in susceptibility to PMR related concentration changes, the ratio of cardiac blood concentration/peripheral blood concentration (C/P) of a drug is an often-used marker of PMR. In this study, we investigated the relationship between different potentially significant variables and the C/P ratios of cocaine, benzoylecgonine (BE) and ecgonine methyl ester (EME) in humans. The aim was to elucidate the mechanisms involved in PMR of these substances and potentially provide guidelines aiding forensic toxicologists in the interpretation of postmortem quantitative results of cocaine and its metabolites. To differentiate between postmortem concentration changes due to redistribution versus degradation of cocaine, the relationships between these variables and metabolite/cocaine ratios were investigated as well.

METHOD

Toxicological results of all postmortem cases that were positive for cocaine, BE and/or EME investigated by the Netherlands Forensic Institute between January 1st 2010 and July 31st 2020 were reviewed. The C/P ratios, BE/cocaine ratios and EME/cocaine ratios were determined for all selected cases. Cocaine, BE and/or EME were quantified in both femoral blood and cardiac blood in a total of 148 cases. Ratios were compared between subgroups by performing either a Mann-Whitney U test or a Kruskal-Wallis test followed by post-hoc Mann-Whitney U test.

RESULTS

A statistically significant difference in C/P ratio of EME was observed between trauma and non-trauma cases with median C/P ratios of 2.03 and 1.57, respectively (p value=0.001). A statistically significant difference in EME/cocaine ratio was observed between the BMI subgroups 18.5 - 25.0 kg/m2 and> 25 kg/m2 with median EME/cocaine ratios of 3.79 and 1.58, respectively (p-value<0.001).

CONCLUSION

Postmortem cocaine concentrations should be interpreted with caution, considering the occurrence of both PMR and postmortem degradation. When interpreting postmortem toxicological results in cocaine-related fatalities, it might prove useful to take the above-mentioned variables into account.

Finding the Lost Dissociation Constant of Electrochemical Aptamer-Based Biosensors

Electrochemical aptamer-based (E-AB) biosensors afford real-time measurements of the concentrations of molecules directly in complex matrices and in the body, offering alternative strategies to develop innovative personalized medicine tools. While different electroanalytical techniques have been used to interrogate E-AB sensors (i.e., cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry) to resolve the change in electron transfer of the aptamer's covalently attached redox reporter, square-wave voltammetry remains a widely used technique due to its ability to maximize the redox reporter's faradic contribution to the measured current. Several E-AB sensors interrogated with this technique, however, show lower aptamer affinity (i.e., μM-mM) even in the face of employing aptamers that have high affinities (i.e., nM-μM) when characterized using solution techniques such as isothermal titration calorimetry (ITC) or fluorescence spectroscopy. Given past reports showing that E-AB sensor's response is dependent on square-wave interrogation parameters (i.e., frequency and amplitude), we hypothesized that the difference in dissociation constants measured with solution techniques stemmed from the electrochemical interrogation technique itself. In response, we decided to compare six dissociation constants of aptamers when characterized in solution with ITC and when interrogated on electrodes with electrochemical impedance spectroscopy, a technique able to, in contrast to square-wave voltammetry, deconvolute and quantify E-AB sensors' contributions to the measured current. In doing so, we found that we were able to measure dissociation constants that were either separated by 2-3-fold or within experimental errors. These results are in contrast with square-wave voltammetry-measured dissociation constants that are at the most separated by 2-3 orders of magnitude from ones measured by ITC. We thus envision that the versatility and time scales covered by electrochemical impedance spectroscopy offer the highest sensitivity to measure target binding in electrochemical biosensors relying on changes in electron-transfer rates.

Development of a rapid, in-situ analysis method using sheath-flow probe electrospray ionisation-mass spectrometry for the direct identification of cocaine metabolites in dried blood spots

RATIONALE

Small amounts of biofluid samples are frequently found at crime scenes; however, existing gold standard methods such as LC-MS frequently require destructive extraction of the sample before a time-consuming analysis which puts strain on forensic analysis providers and can preclude further sample analysis. This study presents the application of sheath-flow probe electrospray ionization-mass spectrometry (sfPESI-MS) to the direct analysis of drug metabolites in dried blood spots (DBS) as a high throughput, minimally destructive alternative.

METHODS

A rapid direct analysis method using a sfPESI ionisation source coupled to an Orbitrap Exactive mass spectrometer was applied to detect cocaine metabolites (benzoylecgonine, BZE, cocaethylene, CE, and ecgonine methyl ester, EME) from DBS. An optimisation study exploring the use of different chemical modifiers (formic acid and sodium acetate) in the sfPESI probe extraction solvent was conducted to enhance the sensitivity and reproducibility of the sfPESI-MS method.

RESULTS

Optimisation of the extraction solvent significantly enhanced the sensitivity and reproducibility of the sfPESI-MS method. A quantitative response over a five-point calibration range 0.5 to 10 μg/ml was obtained for BZE (R²  = 0.9979) and CE (R²  = 0.9948). Limits of detection (LOD) of 1.31, 0.29 and 0.15 μg/ml were achieved for EME, BZE and CE, respectively, from 48 h aged DBSs with % RSD (relative standard deviation) across the calibration range ranging between 19%-28% for [BZE + H]⁺ , 13%-21% for [CE + H]⁺ and 12%-29% for [EME + H]⁺ .

CONCLUSIONS

A rapid (< 20 s) quantitative method for the direct analysis of cocaine metabolites from DBS which requires no prior sample preparation was developed. Although the LOD achieved for BZE (LOD: 0.29 μg/ml) was above the UK threshold limit of exposure for drug driving (0.05 μg/ml), the method may be suitable for use in identifying overdose in forensic analysis.

Metabolites of Cannabis Induce Cardiac Toxicity and Morphological Alterations in Cardiac Myocytes

Cannabis is one of the most commonly used recreational drugs worldwide. Rrecent epidemiology studies have linked increased cardiac complications to cannabis use. However, this literature is predominantly based on case incidents and post-mortem investigations. This study elucidates the molecular mechanism of Δ9-tetrahydrocannabinol (THC), and its primary metabolites 11-Hydroxy-Δ9-THC (THC-OH) and 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (THC-COOH). Treatment of cardiac myocytes with THC-OH and THC-COOH increased cell migration and proliferation (p < 0.05), with no effect on cell adhesion, with higher doses (250–100 ng/mL) resulting in increased cell death and significant deterioration in cellular architecture. Conversely, no changes in cell morphology or viability were observed in response to THC. Expression of key ECM proteins α-SMA and collagen were up-regulated in response to THC-OH and THC-COOH treatments with concomitant modulation of PI3K and MAPK signalling. Investigations in the planarian animal model Polycelis nigra demonstrated that treatments with cannabinoid metabolites resulted in increased protein deposition at transection sites while higher doses resulted in significant lethality and decline in regeneration. These results highlight that the key metabolites of cannabis elicit toxic effects independent of the parent and psychoactive compound, with implications for cardiotoxicity relating to hypertrophy and fibrogenesis.

Immobilization Strategies for Enhancing Sensitivity of Electrochemical Aptamer-Based Sensors

Electrochemical aptamer-based (E-AB) sensors are a versatile sensing platform that can achieve rapid and robust target detection in complex matrices. However, the limited sensitivity of these sensors has impeded their translation from proof-of-concept to commercial products. Surface-bound aptamers must be sufficiently spaced to bind targets and subsequently fold for signal transduction. We hypothesized that electrodes fabricated using conventional methods result in sensing surfaces where only a fraction of aptamers are appropriately spaced to actively respond to the target. As an alternative, we presented a novel aptamer immobilization approach that favors sufficient spacing between aptamers at the microscale to achieve optimal target binding, folding, and signal transduction. We first demonstrated that immobilizing aptamers in their target-bound, folded state on gold electrode surfaces yields an aptamer monolayer that supports greater sensitivity and higher signal-to-noise ratio than traditionally prepared E-AB sensors. We also showed that performing aptamer immobilization under low ionic strength conditions rather than conventional high ionic strength buffer greatly improves E-AB sensor performance. We successfully tested our approach with three different small-molecule-binding aptamers, demonstrating its generalizability. On the basis of these results, we believe our electrode fabrication approach will accelerate development of high-performance sensors with the sensitivity required for real-world analytical applications.

Cocaine Induces Cytoskeletal Changes in Cardiac Myocytes: Implications for Cardiac Morphology

Cocaine is one of the most widely abused illicit drugs worldwide and has long been recognised as an agent of cardiac dysfunction in numerous cases of drug overdose. Cocaine has previously been shown to up-regulate cytoskeletal rearrangements and morphological changes in numerous tissues; however, previous literature observes such changes primarily in clinical case reports and addiction studies. An investigation into the fundamental cytoskeletal parameters of migration, adhesion and proliferation were studied to determine the cytoskeletal and cytotoxic basis of cocaine in cardiac cells. Treatment of cardiac myocytes with cocaine increased cell migration and adhesion (p < 0.05), with no effect on cell proliferation, except with higher doses eliciting (1–10 μg/mL) its diminution and increase in cell death. Cocaine downregulated phosphorylation of cofilin, decreased expression of adhesion modulators (integrin-β3) and increased expression of ezirin within three hours of 1 μg/mL treatments. These functional responses were associated with changes in cellular morphology, including alterations in membrane stability and a stellate-like phenotype with less compaction between cells. Higher dose treatments of cocaine (5–10 μg/mL) were associated with significant cardiomyocyte cell death (p < 0.05) and loss of cellular architecture. These results highlight the importance of cocaine in mediating cardiomyocyte function and cytotoxicity associated with the possible loss of intercellular contacts required to maintain normal cell viability, with implications for cardiotoxicity relating to hypertrophy and fibrogenesis.

Toxicological analysis of serious drug-related harm among electronic dance music festival attendees in New South Wales, Australia: A consecutive case series

BACKGROUND

A substantial increase in drug-related harm was observed during the 2018-2019 music festival season in New South Wales, Australia, including the deaths of five young people. As part of a rapid public health response, the New South Wales Ministry of Health referred samples from patients with suspected severe drug-related illness for forensic toxicological testing to identify the type and concentration of substances associated with the presentations.

METHODS

Cases were identified through a variety of active and passive surveillance systems, and selected consecutively based on indicators of clinical severity. Comprehensive toxicology testing of blood and urine samples was expedited for all cases. Demographic and clinical characteristics were collated, together with quantitative toxicology results. Results were analysed using descriptive statistics.

RESULTS

Forty cases from eleven different music festivals were included. The majority of cases (80.0%) were aged 25 years and under. There were five fatalities, and 62.5% of cases were admitted to intensive care units. MDMA was the most frequent substance, detected in 87.5% of cases. In 82.9% of cases with MDMA, blood concentrations were above thresholds that have been associated with toxicity. Multiple substances were detected in 60.0% of cases. Novel psychoactive substances were not detected.

CONCLUSIONS

Our findings strongly suggest that MDMA-related toxicity was a major factor in the severity of the clinical presentations among these cases. Other substances may have enhanced MDMA toxicity but appear unlikely to have caused severe toxicity in isolation. These findings have important implications for harm reduction strategies targeted to music festival settings.

Four cases of death involving the novel synthetic cannabinoid 5F-Cumyl-PEGACLONE

Purpose

Cumyl-PEGACLONE was the first synthetic cannabinoid (SC) with a γ-carbolinone core structure detected in forensic casework and, since then, it has dominated the German SC-market. Here the first four cases of death involving its fluorinated analog, 5F-Cumyl-PEGACLONE, a recently emerged γ-carbolinone derived SC, are reported.

Methods

Complete postmortem examinations were performed. Postmortem samples were screened by immunoassay, gas chromatography mass spectrometry (GC–MS) or liquid chromatography tandem mass spectrometry. For quantification of SCs, the standard addition method was employed. Herbal blends were analyzed by GC–MS. In each case of death, the Toxicological Significance Score (TSS) was assigned to the compound.

Results

5F-Cumyl-PEGACLONE was identified at concentrations ranging 0.09–0.45 ng/mL in postmortem femoral blood. In case 1, signs of hypothermia and kidney bleedings were noted. Despite a possible tolerance due to long term SC use, a TSS of 3 was assigned. In case 2, an acute heroin intoxication occurred and a contributory role (TSS = 1) of 5F-Cumyl-PEGACLONE was suggested. In case 3, a prisoner was found dead. GC–MS analysis of herbal blends, retrieved in his cell together with paraphernalia, confirmed the presence of 5F-Cumyl-PEGACLONE and a causative role was deemed probable (TSS = 2). In case 4, the aspiration of gastric content due to a SC-induced coma was observed (TSS = 3).

Conclusions

5F-Cumyl-PEGACLONE is an emerging and extremely potent SC which raises serious public health concerns. A comprehensive analysis of circumstantial, clinical, and postmortem findings, as well as an in-depth toxicological analysis is necessary for a valid interpretation and for the assessment of the toxicological significance.

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.

Alcohol in combination with illicit drugs among fatal injuries in Sao Paulo, Brazil: An epidemiological study on the association between acute substance use and injury

Injury deaths have a major impact on public health systems, particularly in the Latin American region; however, little is known about how different drugs, in combination or not with alcohol, interact with each injury type. We tested an epidemiological protocol for investigating alcohol and other drug acute use among fatally injured victims taking into account the injury context for all injury causes in Sao Paulo, Brazil. Blood alcohol and drug content were fully screened and confirmed following a probability sample selection of decedents (n = 365) during 19 consecutive months (2014-2015). Drug concentrations, including benzodiazepines, cannabis, cocaine, and opioids were determined by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography tandem mass spectrometry (LC-MS/MS). Toxicology data were interpreted in combination with injury context retrieved from police records regarding cause, place of injury, and victims' criminal history. More than half of all fatally injured victims studied were under the influence of at least one substance (55.3%). Alcohol was the leading substance consumed before a fatal injury event (30.1%), followed by cocaine (21.9%) and cannabis (14%). Illicit drug use (cocaine and cannabis) comprised more than two thirds of all drug-related deaths. Alcohol-positive deaths are over-represented among road traffic injuries, while drug-positive deaths are more prevalent among intentional injuries. Victims who had previous criminal convictions were significantly more likely to have used illicit drugs compared to those who did not have a criminal background. We estimated that one in every two fatal injuries in the city of Sao Paulo is associated with acute substance use by the victim. The health burden attributed to alcohol- and drug-related fatal injury events has reached significant higher levels in Latin American cities such as Sao Paulo compared globally.

Ethanol addictively enhances the in vitro cardiotoxicity of cocaine through oxidative damage, energetic deregulation, and apoptosis

Cocaine (COC) is frequently consumed in polydrug abuse settings, and ethanol (EtOH) is the most prominent co-abused substance. Clinical data and experimental evidence suggest that the co-administration of COC with EtOH can be more cardiotoxic than EtOH or COC alone, but information on the molecular pathways involved is scarce. Since these data are crucial to potentiate the identification of therapeutic targets to treat intoxications, we sought to (i) elucidate the type of interaction that occurs between both substances, and (ii) assess the mechanisms implicated in the cardiotoxic effects elicited by COC combined with EtOH. For this purpose, H9c2 cardiomyocytes were exposed to COC (104 µM-6.5 mM) and EtOH (977 µM-4 M), individually or combined at a molar ratio based on blood concentrations of intoxicated abusers (COC 1: EtOH 9; 206 µM-110 mM). After 24 h, cell metabolic viability was recorded by the MTT assay and mixture toxicity expectations were calculated using the independent action (IA) and concentration addition (CA) models. EtOH (EC₅₀ 305.26 mM) proved to act additively with COC (EC₅₀ 2.60 mM) to significantly increase the drug in vitro cardiotoxicity, even when both substances were combined at individually non-cytotoxic concentrations. Experimental mixture testing (EC₅₀ 19.18 ± 3.36 mM) demonstrated that the cardiotoxicity was fairly similar to that predicted by IA (EC₅₀ 22.95 mM) and CA (EC₅₀ 21.75 mM), supporting additivity. Concentration-dependent increases of intracellular ROS/RNS and GSSG, depletion of GSH and ATP, along with mitochondrial hyperpolarization and activation of intrinsic, extrinsic, and common apoptosis pathways were observed both for single and combined exposures. In general, the mixture exhibited a toxicological profile that mechanistically did not deviate from the single drugs, suggesting that interventions such as antioxidant administration might aid in the clinical treatment of this type of polydrug intoxication. In a clinical perspective, the observed additive mixture effect may reflect the increased hazards at which users of this combination are exposed to in recreational settings.

Effects of drugs of abuse on channelrhodopsin-2 function

Channelrhodopsins are light activated ion channels used extensively over the past decade to probe the function of genetically defined neuronal populations and distinct neural circuits with high temporal and spatial precision. The widely used Channelrhodopsin-2 variant (ChR2) is an excitatory opsin that undergoes conformational changes in response to blue light, allowing non-selective passage of protons and cations across the plasma membrane thus leading to depolarization. In the addiction neuroscience field, opsins such as ChR2 provide a means to disambiguate the overlapping circuitry involved in mediating the reinforcing and aversive effects of drugs of abuse as well as to determine the plasticity that can occur in these circuits during the development of dependence. Although ChR2 has been widely used in animal models of drug and alcohol self-administration, direct effects of drugs of abuse on ChR2 function may confound its use and lead to misinterpretation of data. As a variety of neuronal ion channels are primary targets of various drugs of abuse, it is critical to determine whether ChR2-mediated currents are modulated by these drugs. In this study, we performed whole-cell electrophysiological recordings in HEK293 cells expressing the commonly used ChR2(H134R) variant and examined the effects of various drugs of abuse and other commonly used agents on light-induced currents. We found no differences in ChR2-mediated currents in the presence of 30 μM nicotine, 30 μM cocaine, 100 μM methamphetamine or 3 mM toluene. Similarly, ChR2 currents were insensitive to 30 mM ethanol but higher concentrations (100-300 mM) produced significant effects on the desensitization and amplitude of light-evoked currents. Tetrahydrocannabinol (1-10 μM) and morphine (30-100 μM) significantly inhibited ChR2 currents while the cannabinoid receptor antagonist AM-251 had no effect. The sodium channel blocker tetrodotoxin (5 μM) and the generic channel blocker/contrast agent gadolinium chloride (10 mM) also reduced ChR2 currents while the divalent ion magnesium (10 mM) had no effect. Together, the results from this study highlight the importance of conducting appropriate control experiments when testing new compounds in combination with optogenetic approaches.

Cocaine Constrictor Mechanisms of the Cerebral Vasculature

Cocaine constriction of the cerebral vasculature is thought to contribute to the ischemia associated with cocaine use. However, the mechanisms whereby cocaine elicits relevant vasoconstriction remain elusive. Indeed, proposed intra- and intercellular mechanisms based on over 3 decades of ex vivo vascular studies are, for the most part, of questionable relevancy due to the generally low contractile efficacy of cocaine combined with the use of nonresistance-type vessels. Furthermore, the significance attached to mechanisms derived from in vivo animal studies may be limited by the inability to demonstrate cocaine-induced decreased cerebral blood flow, as observed in (awake) humans. Despite these apparent limitations, we surmise that the vasoconstriction relevant to cocaine-induced ischemia is elicited by inhibition of dilator and activation of constrictor pathways because of cocaine action on the neurovascular unit (neuron, astrocyte, and vessel) and on vessels outside the unit. Furthermore, previous cocaine exposure, that is, conditions present in human subjects, downregulates and sensitizes these dilator and constrictor pathways, respectively, thereby enhancing constriction to acute cocaine. Identification of specific intra- and intercellular mechanisms requires investigations in the isolated microvasculature and the neurovascular unit from species chronically exposed to cocaine and in which cocaine decreases cerebral blood flow.