New psychoactive substances: challenges for drug surveillance, control, and public health responses.

The rapid emergence since the mid-2000s of a large and diverse range of substances originally designed as legal alternatives to more established illicit drugs (pragmatically clustered and termed new psychoactive substances; [NPS]) has challenged traditional approaches to drug monitoring, surveillance, control, and public health responses. In this section of the Series, we describe the emergence of NPS and consider opportunities for strengthening the detection, identification, and responses to future substances of concern. First, we explore the definitional complexity of the term NPS. Second, we describe the origins and drivers surrounding NPS, including motivations for use. Third, we summarise evidence on NPS availability, use, and associated harms. Finally, we use NPS as a case example to explore challenges and opportunities for future drug monitoring, surveillance, control, and public health responses. We posit that the current means of responding to emerging substances might no longer be fit for purpose in a world in which different substances can be rapidly introduced, and where people who use drugs can change preferences on the basis of market availability.