Recreational drug use at a major music festival: trend analysis of anonymised pooled urine.

Objective: The spread of new psychoactive substances (NPS) has expanded rapidly in the last decade. The complexity of the pharmacological effects of NPS challenges the traditional treatment guidelines, and information of the emergence of new arrivals is valuable. Our knowledge on the actual range of recreational drugs used and NPS available in Denmark is limited as identification is possible only when consumers become patients in the healthcare system or through drug seizures. We aimed to detect classical recreational drugs and NPS in the urine of music festival attendees and evaluate if the use of NPS could have been predicted by comparing study data with drug seizure data from the previous year published by European and Danish health authorities.

Methods: In a cross-sectional study, 44 urine samples were collected from three urinals at Roskilde Festival 2016-the largest Danish music festival. Two urinals were placed at music stages with late-night concerts, and one urinal was placed at a camp site. Samples were prepared using enzymatic hydrolysis followed by cationic and anionic solid phase extraction, and analysed using ultra performance liquid chromatography-high-resolution time-of-flight mass spectrometry (UPLC-HR-TOF-MS). Data were processed using an in-house library of 467 target substances, including legal and illegal drugs and metabolites. Urine drug-screening immunoassays were also evaluated and results were compared to UPLC-HR-TOF-MS results.

Results: In total, 77 drugs, including metabolites, were qualitatively identified in the 44 urine samples. The recreational drugs identified were amphetamine (n = 30), cocaine (n = 44), MDA (n = 40), MDMA (n = 44), THC-COOH (n = 19) and ketamine (n = 17). No NPS were identified. Sample testing using the urine drug-screening immunoassays showed presence of cocaine (n = 27), methamphetamine/MDMA (n = 4), THC (n = 7), "Spice" (n = 7) and methylphenidate (n = 1). These discrepancies might be caused by differences in cut-off values between the analytical methods, limited specificity or cross-reactivity of the urine drug-screening immunoassays compared to UPLC-HR-TOFMS results.

Conclusion: Widespread uses of classical recreational drugs were identified in pooled urine samples. The prevalence of NPS was not as comprehensive as expected based on the European and Danish health authorities reports on illegal drugs. Urine drug-screening immunoassays results are advised to be confirmed by chromatographic bioanalysis.