Exposures to synthetic cathinones, fentanyl, and xylazine among nightclub attendees in New York City, 2024

Abstract

Background:

Use of party drugs is common among nightclub attendees, but more information is needed regarding both intentional use and unknown exposure to synthetic cathinones, fentanyl, and xylazine in this high-risk population.

Methods:

Throughout 2024, participants attending nightclubs in New York City were surveyed and had their saliva analyzed for drug exposure using targeted and untargeted analysis (n = 1024). We calculated the prevalence of synthetic cathinone, fentanyl, and xylazine exposure overall and in relation to demographic and drug use characteristics.

Results:

11 (1.1 %) tested positive for one or more synthetic cathinones, 1.5 % (n = 15) tested positive for fentanyl or its precursor (4-ANPP), and 4 (0.4 %) tested positive for xylazine. All but one exposure to fentanyl was linked to unreported past-month use (93.3 %) and 54.5 % of synthetic cathinone exposures were linked to unreported past-month use (ps<.05). Three of four participants (75.0 %) testing positive for xylazine also tested positive for fentanyl exposure. Most (n = 8) synthetic cathinone exposures involved methylmethcathinone (MMC), and there were also detections of chloromethcathinone (CMC, n = 4), N-N-dimethylpentylone (n = 2), N-ethylpentylone (n = 2), and eutylone (n = 2). Compared to those testing positive for synthetic cathinones, those testing positive for fentanyl were more likely to identify as heterosexual and/or test positive for prescription opioid use, and less likely to have a college degree or to test positive for MDMA use (ps<.05).

Conclusions:

Unintentional exposure to these drugs is occurring, often because they have been added as adulterants in more common drugs. Results can inform prevention and harm reduction education in this population and in the general population.

1. Introduction

The illicit drug landscape continues to rapidly shift with new psychoactive substances (NPS) continuing to emerge (European Monitoring Centre for Drugs and Drug Addiction, 2024 [EMCDDA]). Novel synthetic opioids such as fentanyl analogs and nitazenes have continued to emerge, and illicitly manufactured fentanyl and other novel opioids have been linked to over 70,000 deaths in the US per year since 2021 (Garnett and Miniño, 2024). Synthetic cathinones continue to emerge, often as adulterants in drugs like ecstasy/Molly (MDMA) (European Monitoring Centre for Drugs and Drug Addiction, 2024; U.S. Drug Enforcement Administration, 2023). Xylazine in particular has emerged as a common adulterant linked to thousands of fentanyl-related overdose deaths (Kariisa et al., 2023). Information on known use and unintentional exposure to these drugs is often lacking because people who use illicit drugs often do not know if their purported drug being used contains adulterant drugs (Evans et al., 2021; Palamar and Salomone, 2023). As such, a combination of self-report and toxicology testing is often needed to determine the prevalence of (unintentional) exposure. Publication of both self-report and toxicology data are also often lagged, focus solely on fatal or nonfatal poisonings or overdoses, and data may not differentiate substances detected or correlates of detection.

Many toxicology studies focus on poisonings, but there has been a lack of data on exposure to NPS among people in high-risk populations that did not necessarily experience adverse events. Such studies can inform us about the prevalence of exposure within specific populations. A combination of self-report and biospecimen testing can not only help determine the prevalence of NPS exposure but it can also help us deduce the prevalence of unintentional exposure (e.g., if an NPS is detected after not being reportedly used). Many of such studies have focused on electronic dance music (EDM) event attendees who are known to be at high risk for unintentional exposure to NPS through drugs such as ecstasy/MDMA (Krotulski et al., 2018a; Palamar and Salomone, 2023; Palamar et al., 2023a, 2023b). While many of our past studies have focused on hair testing in this population, our current study utilizes saliva testing. Determination of drug use by saliva collection has been well established (da Cunha et al., 2021; Desrosiers and Huestis, 2019; Drummer, 2005, 2006; Langel et al., 2008). Saliva is an advantageous biospecimen as it is non-invasive, quick and easy to collect (especially in non-medical settings), and the collection device’s storage container generally contains a stabilizing buffer to help prevent drug loss. The window of detection for drugs in saliva varies (i.e., 5–48 h) and the chemistry of individual drugs can lead to low partitioning of drugs from blood to saliva (Drummer, 2006; Verstraete, 2004). However, these points can become moot because drugs are often ingested orally (or introduced to the mouth during use) creating oral cavity “contamination”, inflating drug concentrations in salvia and assisting in their detection.

In this study, we surveyed and conducted advanced drug testing analysis on saliva samples from EDM nightclub attendees in New York City (NYC) throughout 2024. We focused on this population because they are a sentinel population with respect to trends in party drug use (e. g., ecstasy/MDMA, cocaine), and given their relatively high prevalence of use (Palamar et al., 2023a, 2023b), they allow for rapid detection of both known use and unknown exposure to NPS. Focusing on this population can not only inform prevention and harm reduction information but this can also inform scientists and the public about trends that might begin to emerge in the general population.

2. Methods

2.1. Data source and participants

Adults were surveyed as they were about to enter nightclubs in NYC featuring EDM from January through November 2024. Each week, events were randomly selected based on an ongoing list of nightclubs and EDM events located via an EDM event ticket website and social media monitoring. Recruitment typically occurred on 1–4 nights per week (from Thursday through Sunday). People were eligible if they were aged ≥ 18 years and attending or about to attend the selected event. Participants provided informed consent and then completed a survey (which typically took ~10 min to complete) on a tablet (at the point of recruitment). Study staff asked participants if they were willing to provide a saliva (oral fluid) sample to be analyzed. Salvia was collected using the Quantisal^™ oral fluid collection device (Abbott Laboratories, n.d.). This device contains a cotton pad which is placed in the mouth and there is an indicator that changes color when 1 mL is collected. The collector is then transferred to the storage container which contains 3 mL of a stabilizing buffer. A total of 1465 participants completed the survey (and received compensation of $10 USD for survey completion), and those providing a saliva sample were compensated an extra $10 USD. The response rate for the survey was 67.2 % and among those completing the survey, 1024 participants (a 69.9 % response rate) provided an analyzable saliva sample. It should be noted that we detected some significant differences between those providing and not providing saliva with those with a high less diploma or less, and those reporting past-month/past-day use of cocaine and ketamine more likely to provide a sample (ps<0.05) (Supplemental Table 1). The New York University Langone Medical Center institutional review board approved all study methods.

2.2. Measures

First, the survey asked participants about demographic characteristics, including age, sex, race/ethnicity, education, and sexual orientation. Participants were also asked about their frequency of past-year EDM event attendance. Participants were then asked about past-month (past-30-day) and past-day (past-24-hour) use of various drugs including cocaine, ketamine, ecstasy/MDMA, methamphetamine, prescription opioids (nonmedical use), heroin, fentanyl, other fentanyls (analogs such as carfentanil), and synthetic cathinones. With regard to nonmedical prescription opioid use, they were asked specifically about nonmedical use of Vicodin (or other hydrocodone products), OxyContin (or other oxycodone products; e.g., Percocet, Roxicodone), tramadol, codeine, morphine, Dilaudid (hydromorphone), and methadone. Regarding synthetic cathinones, participants were reminded that these substances are commonly referred to as “bath salts”, and they were asked about use of methylone, Flakka (alpha-PVP), mephedrone (MCAT), butylone, MDPV, ethylone, pentylone, dibutylone, N-ethylpentylone, N-N-dimethylpentylone, and “bath salt unknown”. For both prescription opioids and synthetic cathinones, participants also had an option to type in names of drugs in those classes not specifically queried.

2.3. Saliva analysis

After recruitment each week, saliva samples were mailed at ambient temperature to the laboratory for analysis where they were refrigerated. Testing was performed using previous validated and published methods (Krotulski et al., 2018a, 2018b, 2020). Saliva samples were prepared by basic and acidic liquid-liquid extraction to capture relevant substances of interest. Samples were processed against an in-house library database containing analytical reference data for over 1200 drug targets, including various fentanyls (plus precursors and metabolites; n > 120), novel stimulants and synthetic cathinones (n > 100), many other NPS (n > 600), and more traditional recreational drugs (e.g., benzodiazepines, stimulants, opiates, opioids, hallucinogens, cannabinoids). The scope of testing is provided in Supplemental Table 2. The non-targeted nature of our testing methods allowed for the ability to detect drugs not in our library using sophisticated data processing approaches; however, for confirmation of their presence, standard reference materials are ordered for comparative analysis. Samples were analyzed via liquid chromatography quadrupole time-of-flight mass spectrometry (LC–QTOF–MS) using a SCIEX TripleTOF 5600 + and a SCIEX X5000R. Chromatographic separation was achieved using 10 mM ammonium formate in water, acetonitrile and methanol (50:50, v:v) with 0.1 % formic acid, and a Phenomenex^® Kinetex C18 (50 mm×3.0 mm, 2.6 μm) analytical column. The instrument operated in positive electrospray ionization mode. The TOF-MS scan range was 100–510 Da, the TOF-MS/MS scan range was 40–510 Da, and the collision energy was 35 ± 15 V. The total assay runtime was 15.5 mins. Datafiles were processed against our library with retention time, accurate mass, accurate fragment masses, and MS/MS fragment library spectra generated using standard reference materials. Data processing was conducted using SCIEX PeakView (version 2.2), MasterView (version 1.1), and SciexOS (version 3.4.0). The method was validated according to best practices in forensic toxicology, evaluating accuracy/bias, precision, carryover, interferences, limit of detection, autosampler stability, and recovery (Krotulski et al., 2020; Scientific Working Group for Forensic Toxicology 2013).

2.4. Statistical analysis

We first computed the prevalence of detection of NPS and NPS categories, and we also computed the prevalence of self-reported past-month and past-day use of related drugs. We also computed the correct classification statistics (sensitivity, specificity, and positive and negative predictive value) for NPS and NPS classes detected in comparison to past-month and past-day self-reported use. After categorizing NPS into categories (specifically, synthetic cathinones, fentanyl and its analogs, and xylazine), we described detection of clusters of cases, defined as detection of multiple cases on the same night of recruitment (within the same hour). We then computed descriptive statistics for both the full sample and according to NPS category by demographic and drug use characteristics. Finally, we compared demographic and drug use characteristics between those testing positive for either of the two largest NPS categories (fentanyl and synthetic cathinones) using Fisher’s Exact Test. The two cases testing positive for both classes were excluded from these tests. Data were analyzed using Stata 17 SE (StataCorp, College Station, TX).

3. Results

Regarding detection of synthetic cathinones (Table 1), 11 participants (1.1 % of the sample) tested positive for exposure. The most commonly detected synthetic cathinone was methylmethcathinone (commonly referred to as mephedrone/4-MMC; n = 8, 0.8 %), followed by chloromethcathinone (n = 4, 0.4 %), N-N-dimethylpentylone (n = 2, 0.2 %), N-ethylpentylone (n = 2, 0.2 %), and eutylone (n = 2, 0.2 %). When compared to self-reported use, 25 (2.4 %) reported past-month use of any synthetic cathinones, but of those testing positive for any, 6 (54.5 %) did not report use, compared to 45.5 % testing positive among those reporting use (p < .001). Seven participants (0.7 %) reported past-day use and of those testing positive for exposure to any, 63.6 % (n = 7) did not report past-month use. Five (0.5 %) participants reported past-month pentylone use, one reported N-N-dimethylpentylone use, and one reported N-ethylpentylone use. Of the two participants testing positive for N-N-dimethylpentylone and of the two testing positive for N-ethylpentylone use, none reported past-month use. While 13 participants (1.3 %) reported past-month mephedrone use, 8 tested positive for methylmethcathinone (likely an indicator of “mephedrone” exposure), and of the positive cases, 3 (37.5 %) did not report use.

Table 1.

Prevalence of synthetic cathinone, fentanyl, and xylazine positivity and use according to self-report (n = 1024).

	Positive n (%)	Reported Past-Month Use n (%)	Reported Past-Day Use n (%)
Synthetic Cathinones	11 (1.1)	25 (2.4)	7 (0.7)
Pentylone	0 (0.0)	5 (0.5)	0 (0.0)
N-N-dimethylpentylone	2 (0.2)	1 (0.1)	0 (0.0)
N-ethylpentylone	2 (0.2)	1 (0.1)	0 (0.0)
Eutylone	2 (0.2)	1 (0.1)	0 (0.0)
Mephedrone	–	13 (1.3)	5 (0.5)
Methylmethcathinone	8 (0.8)	–	–
Chloromethcathinone	4 (0.4)	–	–
Methylone	0 (0.0)	1 (0.1)	0 (0.0)
Butylone	0 (0.0)	3 (0.3)	0 (0.0)
MDPV	0 (0.0)	1 (0.1)	0 (0.0)
Alpha-PVP	0 (0.0)	3 (0.3)	1 (0.1)
Ethylone	0 (0.0)	4 (0.4)	1 (0.1)
Dibutylone	0 (0.0)	2 (0.2)	0 (0.0)
“Bath salt” unknown	–	2 (0.2)	0 (0.0)
Fentanyl
Fentanyl (or ANPP)	15 (1.5)	–	–
Fentanyl	14 (1.4)	2 (0.2)	1 (0.1)
4-ANPP	6 (0.6)	–	–
Norfentanyl	4 (0.4)	–	–
para-Fluorofentanyl	3 (0.3)	–	–
Phenethyl–4-ANPP	2 (0.2)	–	–
Xylazine	4 (0.4)	–	–

Note. MDPV = methylenedioxypyrovalerone; alpha-PVP = α-pyrrolidinopentiophenone; 4-ANPP = 4 4-anilino-N-phenethyl-piperidine. Methylmethcathinone positivity indicates use of mephedrone or a similar isomer such as 2-MMC or 3-MMC; the survey specifically asked participants about mephedrone use, not methylmethcathinone use. “–“ indicates that data were not collected.

With regard to detection of exposure to fentanyls (Table 1 continued), 14 (1.4 % of the sample) tested positive for exposure to fentanyl, and 6 (0.6 %) tested positive for 4-anilino-N-phenethyl-piperidine (4-ANPP), with one of these participants not testing positive for fentanyl exposure. When considering this one participant as being exposed to fentanyl, the number increased to 15 (1.5 %). In addition, of those testing positive for fentanyl exposure, 4 (0.4 %) tested positive for norfentanyl, 3 tested positive for para-fluorofentanyl exposure (0.3 %), and 2 (0.2 %) for phenethyl-4-ANPP. Only 2 participants reported past-month fentanyl use and 1 reported past-day use. When comparing positivity to self-reported use, while one participant testing positive reported use (6.7 % of those testing positive), 14 (93.3 %) of those testing positive did not report use (p = .029). Finally, xylazine was detected in four samples (0.4 %), mostly alongside fentanyl, but xylazine use was not queried on the survey so it is unknown if any knowingly used. Table 2 further presents the correct classification statistics. When saliva positivity is compared to self-reported use as a “gold standard”, specificity was nearly perfect (>98 %) for all NPS/NPS classes. Sensitivity tended to be much lower due to unreported (likely unintentional) exposure.

Table 2.

Correct classification of saliva test results with self-reported drug use as “Gold Standard” (n = 1024).

Positive			Self-Report		Sensitivity % (95 % CI)	Specificity % (95 % CI)	PPV % (95 % CI)	NPV % (95 % CI)
			+	−
		+	A	B
		−	C	D
Synthetic cathinones (any): past-month use			5 20	6 993	20.0 (6.8–40.7)	99.4 (98.7–99.8)	45.5 (16.7–76.6)	98.0 (97.0–98.8)
Synthetic cathinones (any): past-day use			4 3	7 1010	57.1 (18.4–90.1)	99.3 (98.6–99.7)	36.4 (10.9–69.2)	99.7 (99.1–99.9)
Pentylone (any related compound): past-month use			0 5	2 1017	0.0 (0.0–52.2)	99.8 (99.3–100.0)	0.0 (0.0–84.2)	99.5 (98.9–99.8)
Pentylone (any related compound): past-day use			0 0	2 1022	–	99.8 (99.3–100.0)	–	100.0 (99.6–100.0)
N-N-Dimethylpentylone: past-month use			0 1	2 1021	0.0 (0.0–97.5)	99.8 (99.3–100.0)	0.0 (0.0–84.2)	99.9 (99.5–100.0)
N-N-Dimethylpentylone: past-day use			0 0	2 1022	–	99.8 (99.3–100.0)	–	100.0 (99.6–100.0)
N-ethylpentylone: past-month use			0 1	2 1021	0.0 (0.0–97.5)	99.8 (99.3–100.0)	0.0 (0.0–84.2)	99.9 (99.5–100.0)
N-ethylpentylone: past-day use			0 0	2 1022	–	99.8 (99.3–100.0)	–	100.0 (99.6–100.0)
Eutylone: past-month use			0 1	2 1021	0.0 (0.0–97.5)	99.8 (99.3–100.0)	0.0 (0.0–84.2)	99.9 (99.5–100.0)
Eutylone: past-day use			0 0	2 1022	–	99.8 (99.3–100.0)	–	100.0 (99.6–100.0)
Methylmethcathinone: past-month use			5 8	3 1008	38.5 (13.9–68.4)	99.7 (99.1–99.9)	62.5 (24.5–91.5)	99.2 (98.5–99.7)
Methylmethcathinone: past-day use			4 1	4 1015	80.0 (28.4–99.5)	99.6 (99.0–99.9)	50.0 (15.7–84.3)	99.9 (99.5–100.0)
Fentanyl: past-month use			1 1	14 1008	50.0 (1.3–98.7)	98.6 (97.7–99.2)	6.7 (0.2–31.9)	99.9 (99.4–100.0)
Fentanyl: past-day use			1 0	14 1009	100.0 (2.5–100.0)	98.6 (97.7–99.2)	6.7 (0.2–31.9)	100.0 (99.6–100.0)

Note. Self-reported use of pentylone, N-N-dimethylpentylone, and N-ethylpentylone use was examined separately and also aggregated into any pentylone compound. Methylmethcathinone positivity indicates use of mephedrone or a similar isomer; the survey specifically asked participants about mephedrone use, not methylmethcathinone use. One case was determined to be exposed to fentanyl due to detection of 4-anilino-N-phenethyl-piperidine (4-ANPP) “–“ indicates that estimate could not be made due to no self-reported use. CI = confidence interval; PPV = positive predictive value; NPV = negative predictive value.

Many exposures were detected in clusters from participants entering nightclubs on the same night. Specifically, of the 15 exposures to fentanyl, 3 were on March 24, 2 were on August 25, and 4 were on October 20, with all participants each night being surveyed within the same hour of each other. Regarding synthetic cathinones, a cluster of 6 participants on March 24 provided a sample that tested positive for one or more synthetic cathinones (within the same hour). All tested positive for methylmethcathinone, with three testing positive for methylmethcathinone only, and three testing positive for this substance plus other synthetic cathinones. Specifically, one additionally tested positive for N,N-dimethylpentylone, eutylone, and chloromethcathinone, another tested positive for eutylone and chloromethcathinone, and another tested positive for chloromethcathinone. Of note, the participant testing positive for four synthetic cathinones also tested positive for fentanyl exposure, as did one participant who only tested positive for methylmethcathinone and no other synthetic cathinones. Regarding the four xylazine-positive samples, two were detected in samples submitted within the same hour on August 25.

Table 3 presents demographic and drug use-related descriptive statistics for the full sample and according to synthetic cathinone, fentanyl, and xylazine positivity. With respect to sample characteristics, the majority of the full sample was aged ≥ 26 (51.4 %), male (54.1 %), and 62.3 % had a college degree or higher. Positivity for cocaine (42.0 %) and ketamine (22.4 %) was particularly prevalent. The majority of participants testing positive for synthetic cathinones, fentanyl, and/or xylazine were aged ≥ 26 and male. Most participants in the full sample and among NPS categories identified as white, although all participants testing positive for xylazine exposure identified as black. In addition, with regard to xylazine, all four participants identified heterosexual and as never attending EDM venues (or only 1–2 times per year). The majority of participants in all NPS groups tested positive for cocaine use, the majority of participants testing positive for fentanyl and/or xylazine exposure tested positive for prescription opioid use, and 3 of 4 participants testing positive for xylazine exposure also tested positive for fentanyl exposure. Over a quarter (26.7 %) of those testing positive for fentanyl exposure also tested positive for 6-monoacetylmorphine (6-MAM; heroin), although only one participant (6.7 %) reported past-month use. It should be noted that the one participant who tested positive for xylazine but not fentanyl also did not test positive for any other drugs and did not report past-month use of other drugs.

Table 3.

Prevalence of synthetic cathinone, fentanyl, and xylazine positivity according to demographic and drug use characteristics (n = 1024).

	Full Sample (n = 1024)	Synthetic Cathinones (n = 11)	Fentanyl (n = 15)	Xylazine (n = 4)
Age
18–25	492 (48.1)	2 (18.2)	7 (46.7)	0 (0.0)
≥ 26	532 (51.9)	9 (81.8)	8 (53.3)	4 (100.0)
Sex
Male	554 (54.1)	6 (54.5)	12 (80.0)	3 (75.0)
Female	470 (45.9)	5 (45.5)	3 (20.0)	1 (25.0)
Race/ethnicity
White	438 (42.8)	6 (54.5)	8 (53.3)	0 (0.0)
Black	140 (13.7)	1 (9.1)	4 (26.7)	4 (100.0)
Hispanic	236 (23.1)	1 (9.1)	2 (13.3)	0 (0.0)
Other/mixed	210 (20.5)	3 (27.3)	1 (6.7)	0 (0.0)
Sexual Orientation
Heterosexual	548 (53.5)	2 (18.2)	12 (80.0)	4 (100.0)
Gay/lesbian	219 (21.4)	3 (27.3)	1 (6.7)	0 (0.0)
Bisexual/other	257 (25.1)	6 (54.5)	2 (13.3)	0 (0.0)
Education
High school or less	165 (16.1)	1 (9.1)	5 (33.3)	2 (50.0)
Some college	222 (21.7)	0 (0.0)	4 (26.7)	2 (50.0)
College degree	490 (47.9)	8 (72.7)	6 (40.0)	0 (0.0)
Graduate school	147 (14.4)	2 (18.2)	0 (0.0)	0 (0.0)
Event Attendance
Never/1x or 2x per year	229 (22.4)	0 (0.0)	5 (33.3)	4 (100.0)
Every few months	209 (20.4)	2 (18.2)	3 (20.0)	0 (0.0)
Every month	177 (17.3)	2 (18.2)	0 (0.0)	0 (0.0)
Every other week	218 (21.3)	1 (9.1)	2 (13.3)	0 (0.0)
Every week or more often	191 (18.7)	6 (54.5)	5 (33.3)	0 (0.0)
Cocaine
Positive	430 (42.0)	9 (81.8)	13 (86.7)	3 (75.0)
Past-month reported use	217 (21.2)	4 (36.4)	4 (26.7)	1 (25.0)
Past-day reported use	120 (11.7)	4 (36.4)	3 (20.0)	1 (25.0)
Ketamine
Positive	229 (22.4)	8 (72.7)	6 (40.0)	0 (0.0)
Past-month reported use	182 (17.8)	5 (45.5)	2 (13.3)	0 (0.0)
Past-day reported use	89 (8.7)	4 (36.4)	2 (13.3)	0 (0.0)
MDMA/Ecstasy
Positive	73 (7.1)	10 (90.9)	4 (26.7)	0 (0.0)
Past-month reported use	147 (14.4)	10 (90.9)	4 (26.7)	0 (0.0)
Past-day reported use	50 (4.9)	7 (63.6)	4 (26.7)	0 (0.0)
Methamphetamine
Positive	23 (2.3)	3 (27.3)	2 (13.3)	0 (0.0)
Past-month reported use	8 (0.8)	0 (0.0)	0 (0.0)	0 (0.0)
Past-day reported use	2 (0.2)	0 (0.0)	0 (0.0)	0 (0.0)
Prescription Opioids
Positive	18 (1.8)	2 (18.2)	9 (60.0)	3 (75.0)
Past-month reported use	17 (1.7)	0 (0.0)	1 (6.7)	0 (0.0)
Past-day reported use	4 (0.4)	0 (0.0)	0 (0.0)	0 (0.0)
Heroin/6-MAM
Positive	4 (0.4)	2 (18.2)	4 (26.7)	1 (25.0)
Past-month reported use	2 (0.2)	0 (0.0)	1 (6.7)	1 (25.0)
Past-day reported use	1 (0.1)	0 (0.0)	1 (6.7)	1 (25.0)
Synthetic Cathinones
Positive	11 (1.1)	11 (100.0)	2 (13.3)	0 (0.0)
Past-month reported use	25 (2.4)	5 (45.5)	0 (0.0)	0 (0.0)
Past-day reported use	7 (0.7)	4 (36.4)	0 (0.0)	0 (0.0)
Fentanyl (or 4-ANPP)
Positive	15 (1.5)	2 (18.2)	15 (100.0)	3 (75.0)
Past-month reported use	2 (0.2)	0 (0.0)	1 (6.7)	1 (25.0)
Past-day reported use	1 (0.1)	0 (0.0)	1 (6.7)	0 (0.0)
Xylazine Positive	4 (0.4)	0 (0.0)	3 (20.0)	4 (100.0)

Note. Fentanyl positivity refers to results indicating detection of fentanyl or 4-anilino-N-phenethyl-piperidine (4-ANPP). MDMA = 3,4-methylenediox-ymethamphetamine; 6-MAM = 6-monoacetylmorphine.

Table 4 compares those who tested positive for fentanyl only and those who tested positive for synthetic cathinones only (excluding the two cases testing positive for both). Those who tested positive for fentanyl were more likely to identify as heterosexual than those who tested positive for synthetic cathinones (92.3 % vs. 22.2 %, p = .001), and those testing positive for synthetic cathinones were more likely to have a college degree or higher than those testing positive for fentanyl (100.0 % vs. 38.5 %, p = .006). Finally, while those testing positive for MDMA were more likely to test positive for synthetic cathinones than fentanyl (88.9 % vs. 15.4 %, p = .002), and those testing positive for fentanyl were more likely to test positive for prescription opioids (i.e., morphine [n = 4], codeine [n = 4], tramadol [n = 2]) than those who tested positive for synthetic cathinones (53.9 % vs. 0.0 %, p = .017).

Table 4.

Comparison of prevalence of fentanyl and synthetic cathinone positivity according to demographic characteristics and other drug positivity (n = 22).

	Fentanyl (n = 13)	Synthetic Cathinones (n = 9)	P
Age			0.165
18–25	6 (46.2)	1 (11.1)
≥ 26	7 (53.9)	8 (88.9)
Sex			0.187
Male	10 (76.9)	4 (44.4)
Female	3 (23.1)	5 (55.6)
Race/ethnicity			0.400
White	6 (46.2)	4 (44.4)
Black	4 (30.8)	1 (11.1)
Other/mixed	3 (23.1)	4 (44.4)
Sexual Orientation			0.001
Heterosexual	12 (92.3)	2 (22.2)
Gay/lesbian	1 (7.7)	3 (33.3)
Bisexual/other	0 (0.0)	4 (44.4)
Education			0.006
Less than college degree	8 (61.5)	0 (0.0)
College degree	5 (38.5)	9 (100.0)
Event Attendance			0.099
Less than monthly	8 (61.5)	2 (22.2)
Monthly or more often	5 (38.5)	7 (77.8)
Drug Positivity
Cocaine	11 (84.6)	7 (77.8)	1.000
Ketamine	4 (30.8)	6 (66.7)	0.192
MDMA	2 (15.4)	8 (88.9)	0.002
Methamphetamine	0 (0.0)	1 (11.1)	0.409
Prescription Opioids	7 (53.9)	0 (0.0)	0.017
6-MAM (heroin)	2 (15.4)	0 (0.0)	0.494
Xylazine	3 (23.1)	0 (0.0)	0.240

Note. Fentanyl positivity refers to results indicating detection of fentanyl or 4-anilino-N-phenethyl-piperidine (4-ANPP). MDMA = 3,4-methylenediox-ymethamphetamine; 6-MAM = 6-monoacetylmorphine.

4. Discussion

In this population known for a high prevalence of party drug use, 1.5 % tested positive for fentanyl, 1.1 % tested positive for one or more synthetic cathinones, and 0.4 % tested positive for xylazine exposure. The majority of exposures were linked to unreported use which suggests unintentional exposure. This suggests that although not highly prevalent, exposures to potentially dangerous NPS in this population does occur.

The 1.1 % of participants testing positive for fentanyl is of concern because 93.3 % of those testing positive did not report use. In a previous study of this population, 0.9 % of participants had their hair test positive for fentanyl exposure, although detection in hair can indicate exposure months earlier (Palamar and Salomone, 2023). 4-ANPP, a precursor indicating illicit manufacture of the fentanyl consumed, and phenethyl-4-ANPP, a newer fentanyl byproduct (Schueler, 2017; Vandeputte et al., 2022), were also detected in some fentanyl-positive cases. One participant tested positive for 4-ANPP but not fentanyl, and we considered this case positive for fentanyls. 4-ANPP is rarely detected without the presence of fentanyl, but this does happen in fentanyl-related poisonings (Banta-Green, 2017; Danaceau et al., 2020). Some participants also tested positive for norfentanyl, a metabolite of fentanyl (Shell et al., 2024), and/or para-fluorofentanyl (Papsun et al., 2024). This fentanyl analog was first linked to at least 177 deaths in the US in 2020 and over 3000 in 2023 (Centers for Disease Control and Prevention, 2024). However, this analog is estimated to be three-times less potent than fentanyl, and it is almost always co-detected with fentanyl (NPS Discovery, 2024), as it was in this study. While the extent to which fentanyls being intentionally used or unintentionally used as adulterants is unknown, most of these participants tested positive for cocaine use (86.7 %), 26.7 % tested positive for 6-MAM (heroin), and detection of other drugs was also common. Heroin use is rare in this population (<1 % past-year prevalence) (Palamar et al., 2023a, 2023b), and while heroin is known to be the main drug adulterated with fentanyl (Lim et al., 2024), cocaine can also contain fentanyl (Di Trana et al., 2022; Park et al., 2021). Knowledge that cocaine can contain fentanyl has increased in this population (Palamar, 2023) but more research is needed to determine whose cocaine is most likely to contain fentanyl. We suspect that certain areas and populations are more likely to have fentanyl in their cocaine or other drugs than others.

Synthetic cathinones were detected in specimens submitted by 1.1 % of the sample, although 2.4 % of the sample reported past-month use. However, among those testing positive, 54.5 % did not report use. Within this same population, among those who used ecstasy, in 2015, butylone was the most commonly detected synthetic cathinone, followed by methylone and alpha-PVP, and 2016, the most common compound detected again was butylone, followed by ethylone, pentylone, methylone, and alpha-PVP (Palamar et al., 2016; Palamar et al., 2017). Within this time period, other studies of the dance festival-attending population (in Florida) detected similar compounds in the saliva of people who used ecstasy, but these studies also detected dibutylone, N-ethylpentylone, and dimethylone (Mohr et al., 2020). The prevalence of synthetic cathinone detection in this population decreased from 27.8 % in 2016 to 0.0 % in 2022 (Palamar et al., 2023a, 2023b). Detection of synthetic cathinones is not as common in this population as it was years ago, but results from this sentinel population suggest that synthetic cathinone adulteration has returned, although it is not as prevalent as a decade ago.

The most commonly detected synthetic cathinone in this study was methylmethcathinone, followed by chloromethcathinone, N-N-dimethylpentylone, N-ethylpentylone, and eutylone. While many exposures appear to have been unintentional, most participants testing positive for methylmethcathinone reported past-month use of mephedrone (4-MMC), likely indicating that most use was intentional. A few participants reported past-month pentylone use, but these were not the same participants who tested positive for pentylone-related compounds. Methylmethcathinone being the most prevalent synthetic cathinone was surprising given that this substance has not been common in the US. This drug was prevalent in Europe beginning in about 2008, commonly sold as ecstasy and used for “chemsex”, although toxicology and drug submission data suggest that this drug has largely disappeared in the US since about 2019 (Coronado-Muñoz et al., 2024; European Monitoring Centre for Drugs and Drug Addiction, Europol, 2010; U.S. DEA, 2023; NPS Discovery, 2024). Given that this drug was detected in clusters, it is possible that one or more individuals ordered the drug and knew what drug they were using and distributing. Chloromethcathinone appears to be rare in the past few years (U.S. DEA, 2023; World Health Organization, 2023) which is why we were not expecting to detect this drug. In fact, we may be the first to ever detect this drug in biospecimens in the US which led us to issue a public alert about its presence in the US (Walton et al., 2024). N,N-dimethylpentylone is currently shown to be the most prevalent synthetic cathinone in the US (U.S. DEA, 2023; NPS Discovery, 2024), and N-ethylpentylone and eutylone were also prevalent in recent years but prevalence plummeted in or around 2023 (U.S. DEA, 2023; NPS Discovery, 2024). It is unknown whether these results suggest that such substances or new isomers are returning. Historically, synthetic cathinone exposure has been linked to ecstasy/MDMA use (Di Trana et al., 2022; Palamar et al., 2016; Palamar et al., 2017) and this was a finding of this study. More research is needed to continue to determine the extent to which people are being exposed via adulteration. Nonetheless, this population serves as an ideal sentinel population for monitoring synthetic cathinone exposures.

The sample sizes for participants with detection of fentanyl and synthetic cathinones were large enough and mutually exclusive enough to conduct statistical comparisons. Results suggest that those who used fentanyl were more likely to be heterosexual and to test positive for prescription opioid use. Those testing positive for synthetic cathinones were more likely to have a college degree and to test positive for MDMA. This suggests that at least in this population, these two groups of substances are “different animals” with somewhat different classifications of people who use. This can help further guide prevention and harm reduction efforts.

Finally, with respect to NPS detection, xylazine was detected in four cases, three of which were co-exposed to fentanyl. This should not be surprising as this veterinary tranquilizer has become a common adulterant in fentanyl. Specifically, xylazine rapidly began appearing in overdose mortality cases in 2019 (Kariisa et al., 2021) and increased through 2022, and in June 2022, it was detected in 10.9 % of fentanyl-related deaths (Kariisa et al., 2023). The case of xylazine exposure that was not linked to other drug use (detected or self-reported) was surprising. This case was also not involved in a detected cluster of use, but external exposure cannot be ruled out. Detection of xylazine without co-detection of fentanyl is rare, with one study finding that in 0.5 % of cases, it was co-detected with cocaine but not fentanyl (Quijano et al., 2023). Other studies suggest that xylazine is sometimes detected as an adulterant in drugs such as methamphetamine (Evans et al., 2021). We cannot rule out differences in detection windows for xylazine vs. fentanyl, nor can we assess additional complicating factors such as unknown time of ingestion, route of administration, and dose. All participants testing positive for xylazine were black, heterosexual, and infrequent attendees of EDM events. It is unknown how representative these individuals are of the EDM party-attending population, but this suggests that such studies can also reach people who may not normally frequent such scenes.

4.1. Limitations

Results may not be generalizable to other areas or other populations but results can indeed inform monitoring within these populations. It is unknown to what extent people were unknowingly exposed to NPS (or other drugs) as unintentional exposure was deduced by comparing positivity to survey responses; it is possible that not everyone answered the survey accurately or honestly. Saliva testing can typically only detect recent exposure (e.g., in the past ≤48 h) (Verstraete, 2004) so biological results represent very recent exposure. Relatedly, various drugs can have different detection windows and ability to detect exposure depends on other factors such as how and when the drug was used. Moreover, as time increases between use and collection, drugs fall below analytical detection limits – this can create differences in drugs detected vs. those consumed in concert (e.g., if fentanyl and xylazine are consumed together with xylazine in higher amounts, the xylazine may be detectable for longer due not only to the window of detection but also the detection limit as the fentanyl was at a lesser concentration). We also could not differentiate between different isomers of MMC (e.g., 2-MMC, 3-MMC, 4-MMC) or CMC (e.g., 2-CMC, 3-CMC, 4-CMC). Those with a high school diploma or less, and those reporting past-month/past-day use of cocaine and ketamine were more likely to provide a salvia sample and this can bias findings. Finally, detection of recent NPS exposure was relatively rare. Comparisons of participant characteristics between those exposed to fentanyl vs. those exposure to synthetic cathinones were under-powered (making Type II error a particular concern), but we were still able to uncover multiple significant differences.

4.2. Conclusions

The EDM nightclub-attending population is a high-risk population regarding party drug use and this population can assist in the monitoring of intentional use and unintentional exposure to NPS such as synthetic cathinones, fentanyl, and xylazine. Unintentional exposure to these drugs of drug groups is occurring, likely because they have been added as adulterants in more common drugs. Results can inform prevention and harm reduction education.

Supplementary Material

Appendix A. Supporting information

Supplementary data associated with this article can be found in the online version at doi:10.1016/j.drugalcdep.2025.112792.