RESUMEN

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 (ß = 0.03, P = 0.012), cocaine (ß = 0.08, P < 0.001) and methamphetamine (ß = 0.15, P = 0.028) were statistically significantly higher in strength than substances from off-line sources. Conversely, MDMA tablets (ß = -0.01, P = 0.043) and amphetamine (ß = -0.07, P < 0.001) from cryptomarkets were statistically significantly lower in strength than from off-line sources. MDMA powder (AOR = 0.53, CI = 0.33-0.86) and cocaine (AOR = 0.66, CI = 0.55-0.79) were statistically significantly less likely to be adulterated if sourced from cryptomarkets. However, amphetamine (AOR = 1.54, CI = 1.25-1.90) and LSD (AOR = 1.31, CI = 1.00-1.71) were found to be more likely to be adulterated when purchased from cryptomarkets. Cocaine from cryptomarkets exhibited fewer adulterants (incidence rate ratio = 0.71, CI = 0.60-0.85). CONCLUSION: The relationship between on-line drug market-places and substance quality varies depending on both the specific substance and the dynamics of the cryptomarket.