Adulteration and substitution of drugs purchased in Australia from cryptomarkets: An analysis of Test4Pay

Introduction: Prohibited drugs in unregulated markets may be adulterated, resulting in increased risks for people who use drugs. This study investigated levels of drug adulteration and substitution of drugs purchased in Australia from cryptomarkets. Methods: Data were collected from a darknet forum called Test4Pay from 1 September 2022 to 23 August 2023. Posts were included if they reported the results of drug samples submitted by post to the Vancouver-based Get Your Drugs Tested service, which uses Fourier-transform infrared spectroscopy with immunoassay strip tests (fentanyl and benzodiazepines). Results: Of 103 samples, 65% contained only the advertised substance, 14% contained the advertised substance in combination with other psychoactive and/or potentially harmful substances and for 21%, the advertised substance was absent. Substances sold as MDMA, methamphetamine or heroin were consistently found to contain only the advertised substance, while substances sold as 2C-B, alprazolam or ketamine were the most likely to be completely substituted. Only 4 samples sold as cocaine contained solely the advertised substance, with 13 containing cocaine with adulterants like lidocaine, creatine, levamisole and boric acid (n = 19). No fentanyl contamination was detected. Novel dissociatives and novel benzodiazepines were detected, as well as a nitazene compound. Discussion and Conclusions: Drug markets under prohibition continue to contain numerous unexpected substances, some of which can elevate risk of harm. Cryptomarkets are not immune to this problem, despite review systems, which should, in theory, make vendors more accountable for the quality of their stock. These findings demonstrate a need for expansion of local drug checking services in Australia.