How the recreational stimulant market has changed: Case study in Adelaide, Australia 2016-2019.

The human consumption of stimulant drugs is known to increase over festive periods. In this work, four illicit stimulants: 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA), cocaine and methamphetamine and three new psychoactive substances (NPS): ethylone, mephedrone and N-ethylpentylone were monitored in influent wastewater over the Christmas-New Year period in South Australia from 2016 to 2019 using liquid chromatography-mass spectrometry. The differences in Christmas - New Year consumption between years were evaluated and daily mass loads were compared to the average for that year to determine drug levels over the festive period. Although MDMA, MDA and cocaine showed year-on-year increases, the use over the New Year period was far higher than over the rest of the year, consistent with recreational drug use. These were also the drugs that were used predominantly on weekends during the year. Methamphetamine, which does not have a pattern of predominant weekend use, and the NPS showed variable trends. These results suggest that during holiday periods there are increases in the use of a limited set of drugs only and these can be predicted from patterns of use during the non-holiday periods.