Early identification of the use of potent benzylbenzimidazoles (nitazenes) through wastewater analysis: Two years of data from 22 countries.

Background And Aims: The use of new synthetic opioids, such as the highly potent 2-benzylbenzimidazoles (i.e. nitazene) drugs, is a global health concern because of their increased risk of fatal overdose. In the early 2020s, nitazene analogues were linked to significant numbers of overdoses in the United States. Their reach is now worldwide, with nitazene overdose deaths reported in Europe, Australia and New Zealand. The aim of this study was to measure quantities of nitazenes in wastewater samples collected from 68 locations in 22 countries, covering six continents, to understand and estimate their use.

Methods: Untreated influent wastewater samples were collected over a one-week period that included the New Year period in 2022-2023 and 2023-2024. Samples were collected from 22 countries: Australia, Austria, Belgium, Brazil, Canada, Chile, China, Cyprus, Czechia, France, Germany, Greece, Iceland, Italy, New Zealand, Nigeria, Republic of Korea, Slovenia, Spain, Sweden, United Kingdom and United States. Samples were loaded onto solid-phase extraction cartridges in the country of collection and sent to Australia for elution and analysis using sensitive liquid chromatography-mass spectrometry methods.

Results: A total of 683 individual wastewater samples were analysed across the two years: 339 in 2022-2023 and 344 in 2023-2024. Two nitazene analogues-protonitazene and N-pyrrolidino etonitazene (etonitazepyne)-were found in five separate sites in the United States and Australia. In the 2022-2023 period, protonitazene was found in two sites in the United States. The following year, protonitazene was detected in two further sites in the United States, while both protonitazene and etonitazepyne were found in one site in Australia. Protonitazene mass loads ranged between 0.3 mg/day/1000 people and 100 mg/day/1000 people. Etonitazepyne was also found at mass loads between 0.2-2 mg/day/1000 people).

Conclusions: A very high mass load of protonitazene was calculated, using wastewater analysis, for the day of 30 December 2023 in one site in Australia. Etonitazepyne showed the same trend from a lower base. Wastewater-based nitazene surveillance shows promise as a form of both drug early warning and ongoing monitoring of trends in use, especially as a complementary tool to existing surveillance methods.