"NPS [New Psychoactive Substances] is a category of substances that are fast-evolving, typically volatile and often diversified. The category includes different types of substances in terms of their composition, (il)legitimate use and position in the global drug markets. The great majority of NPS are substances that have no legitimate use, and have no established global large and long-standing markets that compare with the controlled 'traditional' drugs, with few exceptions. One is, for example, khat, a plant-based substance that is not under international control but that has a long-established market in some regions of the world. Another exception is the non medical use of two pharmaceuticals that are not under international control: tramadol and ketamine. Technically, these substances meet the definition of NPS but the underlining challenges posed by these substances are different from the large NPS set of substances. For example, tramadol, which has an established use for pain management, shares similarities with other opioids under international control. In the present report, the discussion of trends in tramadol misuse and seizures is included in the chapter on opioids, while ketamine, which is included in the WHO list of essential medicines and used as a local anaesthetic in many settings, is addressed in the present chapter.
"There are multiple ways to categorize NPS, for example, they can be grouped according to origin – whether plant-based or synthetic, according to psychotropic effects, or according to chemical structure."
UNODC, World Drug Report 2022 (United Nations publication, 2022).