Adulteration poses additional unknown risks to the health of people who use illicit drugs. In this study, we sought to determine the extent and nature of adulteration of ‘MDMA’ in circulation at English summer music festivals in 2021, following Brexit, COVID-19 lockdowns and various regulatory changes overseas. At three festivals in 2019 and 2021, 1648 surrendered substances were analysed with Fourier-transform infrared spectroscopy and colourimetric reagents in a mobile laboratory as part of a harm reduction project. Form, mass, appearance and main psychoactive component were recorded. Analytical results were compared to a parallel self-report survey with 1124 attendees at the same events, as part of the annual English Festival Study. In 2019 and 2021, 417 and 377 samples strongly resembling MDMA (e.g. ecstasy tablets) were tested. Detection of MDMA in such samples decreased from 93% to 55% between the two years.

Whilst virtually absent in 2019, synthetic cathinones and caffeine each constituted approximately one fifth of 2021 samples. 4-Chloromethcathinone (4-CMC), 3-methylmethcathinone (3-MMC) and N-ethylbutylone (eutylone) were the most prevalent cathinones detected. In both years, >35% of survey respondents reported use and/or intention to use MDMA on the fieldwork day; ≤1% reported cathinone or caffeine use, suggesting their consumption was predominantly unintentional. The sharp rise in synthetic cathinone prevalence in the summer 2021 UK market coincided with a unique combination of events including Brexit and the reopening of nightlife after 16 months of lockdowns, months ahead of other European nations. Echoing similar periods over the past decade, the cathinone hydra reared its head to satisfy the buoyant demand for MDMA at a time of scarcity, through substitution with substances legally obtainable in the Netherlands at the time of data collection. Alerts issued on social media led to >360,000 engagements, demonstrating extensive public engagement with illicit market monitoring and harm reduction advice.