Wastewater-based monitoring of illicit drugs in Cyprus by UPLC-MS/MS: The impact of the COVID-19 pandemic.

The outbreak and spread of COVID-19 impacted through various ways the lives of millions of humans globally. In this work, wastewater-based epidemiology (WBE) was applied to investigate the effect of the actions taken by the Republic of Cyprus to confine COVID-19 on the use of illicit stimulant drugs. Daily influent samples were collected from the six main wastewater treatment plants (WWTPs) of the country i) before lockdown (3-9 April 2019), ii) during lockdown (21-27 April 2020), iii) during the post-lockdown period (14-20 July 2020), and, iv) during each season of the following year (20-26 April 2021, 19-25 July 2021, 11-17 October 2021, 25 December 2021-2 January 2022), and analyzed for amphetamine, methamphetamine, MDMA and cocaine. In most areas, amphetamine and methamphetamine use was not affected during the confinement period, but as availability of the substances decreased with time, a drop in their use was observed when most restriction measures were eased (up to 9- and 22-fold decrease, respectively). The limitations on social interactions and events during the quarantine period seem to have led to the reduction of MDMA and cocaine and driven a sharp decrease of their use in most areas studied (up to 11 and 6 times lower, respectively). However, the re-opening of activities led to a pronounced consumption increase, reaching maximum daily values of 800 and 2691 mg/1000 inhabitants/day, respectively. In 2021, drug use was re-established to lower levels. The examination of weekly patterns during this year revealed higher weekend use of methamphetamine, MDMA and cocaine. Our results suggest that both the implementation and the easing of COVID-19 related measures affected the availability and the use of drugs. This study also provides the first insight on the consumption of illicit drugs in the Republic of Cyprus during pre-, post- and pandemic times and demonstrates the importance of WBE.