Background: New psychoactive substances (NPS), often referred to as “legal highs” or “designer
drugs”, are derivatives and analogues of existing psychoactive drugs that are introduced in the
recreational market to circumvent existing legislation on drugs of abuse.
Objective: This systematic review aims to gather the state of the art regarding chemical, molecular
pharmacology and toxicological information of opioid class of NPS.
Methods: Chemical, pharmacological, toxicological and clinical effects of opioid class of NPS were
searched in books and in PubMed (U.S. National Library of Medicine) without a limiting period.
Results: Within this class, fentanyl analogues are among the most frequently abused and pose several
clinical concerns and therefore will be thoroughly discussed. Other opioid sub-categories of NPS frequently
misused include AH-7921, MT-45, U-47700, U-50488, desomorphine, mitragynine, tramadol,
tapentadol, salvinorin A and its analogue herkinorin.
Conclusion: Due to inefficient monitoring techniques, as well as limited knowledge regarding the acute
and long-term effects of opioids NPS, further clinical and forensic toxicological studies are required.