"Depressant NPS encompass two main types of CNS depressants: opioids, which cause analgesia, euphoria, drowsiness, and sedation (eg, fentanyl analogues); and benzodiazepines, which have sedative, anxiolytic, hypnotic, muscle-relaxant, and anticonvulsant effects (eg, etizolam, phenazepam).15 These NPS can be sold under their own name, but have also been detected as counterfeit prescription medicines (eg, in tablets or capsules), or adulterated with or sold as more established illicit drugs (eg, in powder form).16 They are mostly swallowed, snorted, or injected. Some depressant NPS are prescribed medicines in some countries (the benzodiazepine NPS etizolam is a prescription drug in Japan)17 or have other legitimate uses (the opioid NPS carfentanil is used as a tranquiliser in veterinary contexts and as a selective radiotracer in positron emission tomography).18"
Amy Peacock, PhD, Raimondo Bruno, PhD, Natasa Gisev, PhD, Prof Louisa Degenhardt, PhD, Prof Wayne Hall, PhD, Roumen Sedefov, MD, et al. New psychoactive substances: challenges for drug surveillance, control, and public health responses. The Lancet. Volume 394, Issue 10209, p1668-1684, November 02, 2019. Published:October 23, 2019.