Urine Drug Tests Indicate Higher Prevalence of Combined Alcohol and Cocaine Use Compared to Alcohol Together with Cannabis or Amphetamine—A Possible Link to Cocaethylene

Abstract

Aim

This retrospective study examined the prevalence of combined ethanol and cocaine use, which produces an enhanced psychoactive effect through formation of the active metabolite cocaethylene, compared to combined use of ethanol and two other common recreational drugs, cannabis and amphetamine, based on urine drug test results.

Methods

The study was based on >30,000 consecutive samples from routine urine drug testing in 2020, and 2627 samples from acute poisonings in the STRIDA project (2010–2016), in Sweden. Drug testing for ethanol (i.e. ethyl glucuronide and ethyl sulfate), cocaine (benzoylecgonine), cannabis (Δ9-THC-COOH) and amphetamine was done by routine immunoassay screening and LC–MS/MS confirmatory methods. Seven samples testing positive for cocaine and ethyl glucuronide were also analyzed for cocaethylene by LC–HRMS/MS.

Results

Among routine samples for which testing of ethanol and cocaine had been requested, 43% tested positive for both substances, compared with 24% for ethanol and cannabis and 19% for ethanol and amphetamine (P < 0.0001). Among the drug-related intoxications, 60% of cocaine-positive samples were also positive for ethanol, compared to 40% for cannabis and ethanol and 37% for amphetamine and ethanol. Cocaethylene was detected (range 1.3–150 μg/L) in all randomly selected samples testing positive for ethanol and cocaine use.

Conclusions

These results, which were based on objective laboratory measures, indicated that combined ethanol and cocaine exposure was more prevalent than expected from drug use statistics. This may relate both to the common use of these substances in party and nightlife settings, and the amplified and prolonged pharmacological effect by the active metabolite cocaethylene.

INTRODUCTION

It is well known that certain combinations of prescription and over-the-counter medications can have harmful side effects together that they do not display alone (Dechanont et al., 2014; Zheng et al., 2018). The same applies to polydrug use of recreational and established drugs of abuse, which is common (Galicia et al., 2019; Helander et al., 2020; Vercoulen and Hondebrink, 2021). A particularly dangerous combination applies to sedatives, e.g. opioids and benzodiazepines, which increases the risk of dangerous overdose effects causing unconsciousness, respiratory depression and death (Hedegaard et al., 2018).

Drugs are usually converted by phase I and phase II reactions to inactive metabolites that are eventually excreted in the urine. What is less well known is that certain combinations of recreational drugs can have an amplified effect, by forming psychoactive metabolites. Ethanol and cocaine combine in the liver by a transesterification reaction catalyzed by carboxylesterases to form cocaethylene (Fig. 1) (Laizure et al., 2003), an active metabolite that is equally potent as cocaine in blocking the reuptake of dopamine at receptor sites (Jones, 2019). Cocaethylene also has a longer elimination half-life and thereby produces both an enhanced and a prolonged drug effect (McCance-Katz et al., 1998; Herbst et al., 2011; Jones, 2019). In the absence of ethanol, cocaine is hydrolyzed to benzoylecgonine, which is inactive (Fig. 1).

Fig. 1.

Cocaine is hydrolyzed by liver carboxylesterases to the inactive metabolite benzoylecgonine. In the presence of ethanol, cocaine and ethanol combine by a transesterification reaction to the active metabolite cocaethylene, which is equally potent as cocaine and has a longer elimination half-life.

Ethanol and cocaine are frequently used in the same social situations such as party and nightlife venues (Feltmann et al., 2021), and users may have experienced that this drug combination evokes an additive euphoric effect, but without knowing the cause. Moreover, this drug combination has been reported to help relieve discomfort associated with tapering or stopping cocaine (Magura and Rosenblum, 2000). However, users may be unaware that there are also health risks associated with combined cocaine and ethanol exposure (EMCDDA, 2021). Compared to cocaine alone, the combination with ethanol is, for example, indicated to be more cardiotoxic by increasing the risk of cardiac arrest, possibly mediated through cocaethylene (Shastry et al., 2022).

This retrospective study examined the prevalence of combined ethanol and cocaine use, compared with concurrent ethanol and cannabis or amphetamine use, the latter being the two most common recreational drugs (Helander and Villén, 2021), based on laboratory results from urine drug testing, to investigate the association between alcohol and cocaine, amphetamine or cannabis use with specific characteristics of the population.

MATERIALS AND METHODS

Data

The study was based on >30,000 consecutive test results for urine samples submitted in 2020 from drug dependence units and other hospital settings for routine drug testing at the Karolinska University Laboratory, Department of Clinical Pharmacology (Stockholm, Sweden). All test results were de-identified, so information about the origin of the samples or the sex and age of the patients was not available. For comparison, test results for 2627 urine samples from analytically confirmed drug-related acute intoxications at emergency departments collected within the Swedish STRIDA project on new psychoactive substances (carried out in 2010–2016) were also examined (Helander et al., 2020).

Laboratory analysis

Urine samples were first subjected to immunochemical screening with CEDIA reagents (Thermo Fisher Scientific) on a DxC 700 AU chemistry analyzer (Beckman Coulter), and the preliminary positive results were confirmed by liquid chromatography–mass spectrometry (LC–MS/MS). Confirmatory urine testing for ethanol (i.e. the metabolites ethyl glucuronide (EtG) and ethyl sulfate (EtS)), cocaine (the metabolite benzoylecgonine), cannabis (the metabolite Δ9-THC-COOH) and amphetamine was done by validated (EWDTS) and accredited (Swedac) in-house methods at the Karolinska University Laboratory. Nationally harmonized cutoffs were applied for benzoylecgonine (150 μg/L in screening and 100 μg/L in confirmation), amphetamine (500 μg/L vs 200 μg/L) and Δ9-THC-COOH (20/25 μg/L vs 10 μg/L) (Hansson et al., 2015). The EtG and EtS cutoffs were 0.5 and 0.1 mg/L, respectively, and for a positive EtG result, the presence of EtS must also be demonstrated (Helander and Beck, 2005; Helander et al., 2010).

Surplus volumes of seven randomly selected urine samples testing positive for ethanol and cocaine use were also analyzed for cocaethylene, using a validated and accredited LC–HRMS/MS multi-analyte method, which is continuously updated with new analytes (Stephanson et al., 2017). The LC–HRMS system was a Dionex UltiMate 3000 HPLC and a Q Exactive Orbitrap HRMS (Thermo Fisher Scientific) operated in positive mode. Three ion transitions were used to confirm peak identity of cocaethylene (m/z 318.16998 > 196.13306 (quantifier), 82.06584 and 150.09179 (qualifiers)) (Johansen and Bhatia, 2007) in calibrators, prepared by spiking drug-negative urine samples with the reference material, and patient samples.

The cocaethylene concentration was estimated by comparison with calibrators, prepared by spiking blank urine with a certified reference material (Chiron AS, Trondheim, Norway), in full scan–extracted ion chromatogram mode (Stephanson et al., 2017). The samples were diluted with a deuterated internal standard and 2 μL injected. The lower quantification limit (LLOQ) employed was ~1 μg/L, and linear results (R > 0.999) were generated up to 1000 μg/L. Acceptance criteria for a positive identification with the multi-analyte method were ± 3 ppm with reference to the theoretical exact mass, a Gaussian peak shape, and an absolute relative retention time versus calibrator within ±0.03 min.

Statistics

Statistical calculations were performed using MedCalc software (Ostend, Belgium).

RESULTS

Among 30,781 consecutive routine urine samples for which testing of cocaine use had been requested, 1631 (5.3%) tested positive for benzoylecgonine. Of the 1631 cases, EtG analysis had been requested for 158 and 68 (43.0%) of these samples tested positive for recent ethanol exposure (Fig. 2). For cannabis, 10,707 out of a total of 49,341 samples (21.7%) tested positive for Δ9-THC-COOH of which 1089 were also tested for EtG with 259 (23.8%) being positive. For amphetamine, 3489 of 40,446 (8.7%) samples tested positive with 128 of 680 (18.8%) also being positive for ethanol exposure. The relative proportion of cases testing positive for combined cocaine and ethanol use was significantly higher (P < 0.0001) compared to combined cannabis and ethanol or amphetamine and ethanol use (Fig. 2).

Fig. 2.

Relative proportions of urine samples from routine drug tests that were examined, and found to be positive, for combined exposure to ethanol (i.e. ethyl glucuronide (EtG) and ethyl sulfate (EtS)) and cocaine (i.e. benzoylecgonine), or ethanol and cannabis (i.e. Δ9-THC-COOH), or ethanol and amphetamine. The prevalence for combined cocaine and ethanol exposure was significantly higher (P < 0.0001) compared to the other two drug combinations.

The STRIDA project included 2627 acute drug-related intoxication cases of which only 20 (~0.8%) urine samples tested positive for cocaine use, and, of these, 12 (60%) also for recent ethanol exposure. Among the 277 cannabis-positive cases, 111 (40%) were positive for combined cannabis and ethanol use, and of 335 amphetamine-positive cases, 125 (37%) were positive for combined amphetamine and ethanol use. Because of the low number of cocaine-positive samples in this population, the higher frequency of combined cocaine and ethanol positive cases compared to ethanol and cannabis or amphetamine did not reach statistical significance (P = 0.13 and 0.07, respectively).

Among urine samples testing positive for both benzoylecgonine (median 5470 μg/L, range 463–17,400 μg/L) and EtG (median 8.9 mg/L, range 1.1–680 mg/L), 7 randomly selected samples were analyzed for cocaethylene, together with 7 samples being positive for benzoylecgonine (median 3580 μg/L, range 157–26,700 μg/L) but negative for EtG (< 0.5 mg/L). The benzoylecgonine concentrations in the two groups were not statistically different (P = 0.14, Mann–Whitney test). Cocaethylene was detected (range 1.3–150 μg/L) in all seven urine samples testing positive for both cocaine and ethanol use. Chromatograms and mass spectra for a calibrator and two cocaethylene positive urine samples (high and low level) are shown in Fig. 3. The two lowest cocaethylene results originated from urine samples with the lowest benzoylecgonine concentrations (< 800 μg/L), although one contained the highest EtG concentration (680 mg/L). The highest cocaethylene concentration (150 μg/L) was found in a sample with both a high benzoylecgonine (17,400 μg/L) and EtG (292 mg/L) concentration. Overall, the cocaethylene values correlated positively with the benzoylecgonine values (R = 0.82, P = 0.012) but not with EtG (R = 0.14, P = 0.73).

Fig. 3.

Chromatograms and mass spectra from LC–HRMS/MS analysis of cocaethylene in urine in full scan–extracted ion chromatogram mode. Results are shown for (A) a calibrator, prepared by spiking blank urine with a certified reference material, and two selected patient samples containing (B) a high and (C) a low cocaethylene level. The HRMS instrument was operated in positive mode and three ion transitions were used to confirm peak identity of cocaethylene (m/z 318.16998 > 196.13306 (quantifier), 82.06584 and 150.09179 (qualifiers)).

DISCUSSION

This observational retrospective study examined the prevalence of combined alcohol (ethanol) and cocaine exposure in comparison to ethanol together with either of two other common recreational drugs, cannabis or amphetamine, based on urine drug test results from two large independent data sets. The analytical targets for each substance (i.e. EtG and EtS for ethanol, benzoylecgonine for cocaine, Δ9-THC-COOH for cannabis and amphetamine) cover a similar time window, corresponding to drug exposure over the last few days (Verstraete, 2004; Helander et al., 2009; Jones, 2019; Martini et al., 2020), indicating that they were suitable for the purpose of the study.

The present objective results confirmed previous results from laboratory investigations (Snenghi et al., 2018) and supported by interview and survey data (Kedia et al., 2007; Liu et al., 2018), that cocaine and ethanol is a popular drug combination, being more common than ethanol together with either cannabis or amphetamine. This would be expected if cocaine had been the second most common recreational drug next to ethanol. However, according to recent results from urine drug testing in the workplace in Sweden, which likely covers a rough mix of the population in terms of age and sex, cannabis has long been the most frequently used illicit drug in the country, and amphetamine consistently more common than cocaine, although cocaine use has shown a steady increase in recent years (Helander and Villén, 2021). On the other hand, next to alcohol, Swedish nightlife attendees, who are generally younger people, mostly reported onsite use of cocaine, followed by amphetamine, MDMA (ecstasy) and cannabis (Feltmann et al., 2022).

The relative frequency difference between combined use of cocaine and ethanol and the other two drug combinations was rather similar in both data sets, but the levels were consistently higher in the STRIDA samples that originated in emergency departments. This was expected, as only analytically confirmed acute drug intoxications were enrolled in the STRIDA project (Helander et al., 2020). The low incidence of cocaine-positive samples in this population may be due to the fact that this project was carried out during 2010–2016 when cocaine appeared to be a less common drug in Sweden and only rarely found in routine urine drug testing (Helander and Villén, 2021).

Drug use is often associated with short-term problems such as increased impulsive and violent behavior and reduced cognitive function. Combined cocaine and ethanol use is indicated to be a particularly dangerous combination both in the short and long term, and a risk factor for trauma, seizures, myocardial infarction, liver damage and acute death (Signs et al., 1996; Andrews, 1997; Pennings et al., 2002; Assi et al., 2022; Tamargo et al., 2022), which may partly be mediated through cocaethylene. The small number of cocaine and alcohol positive urine samples that were tested for cocaethylene in this study were all confirmed to contain measurable but variable levels, consistent with previous observations (Wu et al., 1992; Fiorentin et al., 2017). As a drug test, cocaethylene confirms recent use of both cocaine and ethanol (Jones, 2019), but not use of cocaine alone. Instead, the standard target for urine drug testing of cocaine is benzoylecgonine, which also shows a longer detection time than cocaethylene (Smith et al., 2010). Therefore, although cocaethylene may be useful as a risk indicator for combined cocaine and ethanol toxicity and the severity of clinical manifestations (Wiener et al., 2010; Zucoloto et al., 2021; Shastry et al., 2022), combined urine measurement of benzoylecgonine and EtG/EtS provides similar information in terms of recent use.

CONCLUSION

The results of this retrospective study based on objective laboratory measures in two independent populations indicated that combined ethanol and cocaine use was more prevalent in Sweden than expected from national drug use statistics. Except that both substances are commonly used in party and nightlife settings, a pharmacological reason may be that this drug combination produces a more intense and longer-lasting stimulant effect mediated by the active metabolite cocaethylene. For use in urine drug testing, a positive cocaethylene test confirms recent exposure to both ethanol and cocaine, but the detection time is shorter than for benzoylecgonine, the standard target for urine testing of cocaine. Nevertheless, given the health risks associated with combined ethanol and cocaine exposure, clinical testing for cocaethylene may be useful as an indicator for increased cocaine toxicity.

FUNDING

Karolinska University Laboratory.

CONFLICT OF INTEREST

None.

DATA AVAILABILITY

The data from this study may be made available by the authors upon request.