Comparison of strength and adulteration between illicit drugs obtained from cryptomarkets versus off‐line

Background and aims Drugs sold on cryptomarkets are thought to have lower levels of adulteration and higher strength compared with those sourced off‐line. The present study aimed to determine whether cryptomarket and off‐line‐sourced 3,4‐methylenedioxy‐N‐methamphetamine (MDMA), cocaine, amphetamine, methamphetamine and lysergic acid diethylamide (LSD) differed in adulteration and strength. Design and setting A between‐groups design was used to compare cryptomarket versus off‐line‐sourced drugs. Regression analyses controlling for year and service were conducted. Drug‐checking services were conducted in Spain (Energy Control) and the Netherlands (Drugs Information and Monitoring System). Cases The cases comprised drug samples that underwent drug checking between 2016 and 2021 and were expected to contain MDMA (tablets; n = 36 065; powder: n = 6179), cocaine (n = 11 419), amphetamine (n = 6823), methamphetamine (n = 293) and LSD (n = 1817). Measurements Drugs were measured for (1) matching the advertised substance (i.e. containing any amount of the expected substance); (2) strength; (3) presence of adulteration; and (4) number of adulterants. Findings The expected drug was more likely to be identified when sourced from cryptomarkets versus off‐line for MDMA tablets [adjusted odds ratio (AOR) = 2.10, 95% confidence interval (CI) = 1.28–3.43], MDMA powder (AOR = 2.64, CI = 1.55–4.51), cocaine (AOR = 3.65, CI = 1.98–6.71) and LSD (AOR = 1.75, CI = 1.13–2.72). Cryptomarket‐sourced MDMA powder (β = 0.03, P = 0.012), cocaine (β = 0.08, P