Background: Two novel synthetic opioids, MT-45 and AH-7921, with mostly undocumented effects and risks, have emerged on the expanding market for recreational drugs on the Internet. The aim of the present study was to characterize the experiences of AH-7921 and MT-45 as described by the users on international drug discussion forums.

Methods: A systematic data search resulted in 96 self-reports which were collected from the leading edge resources of drug related information online. The data were analysed qualitatively using thematic analysis.

Results: The experiences of MT-45 and AH-7921 were characterized by the following themes: (1) Administration of the substances, (2) Well-being and energy, (3) Sedation and reduced here-and-now awareness, (4) Tolerance and withdrawal effects, (5) Side effects, (6) Evaluation of the effects, (7) Increased appreciation, sociableness and intimacy and (8) Self-medication. The experiences appeared to include not only the general and expected opioid effects like withdrawal, analgesia, euphoria, cough suppression, fatigue, constipation, itching, involuntary muscle spasm, nausea and pupillary constriction but also a noteworthy increase in energy. Furthermore, the users also experienced reduced inhibition and a facilitation of social situations. The results also showed that users engaged in different forms of self-medicating behaviour aimed at reducing pain or withdrawal symptoms from traditional opioid use.

Conclusion: The spread of unpredictable, potent and novel opioids constitutes a public health concern which needs to be further monitored in order to minimize potential harm.