New psychoactive substances (NPS) in the Netherlands: occurrence in forensic drug samples, consumer drug samples and poisons center exposures between 2013 and 2017

Background and Aims Although European-wide data on the new psychoactive substances (NPS) drug market are available, country-specific data are limited. We studied recent NPS trend data relative to all recreational drugs on the Dutch drugmarket. Design National observational study. Setting The Netherlands. Data sources Three national indicators were used between 2013 and 2017: (1) forensic drug samples offered to the Netherlands Forensic Institute (NFI); (2) drug samples submitted by consumers to the Drugs Information and Monitoring System (DIMS); and (3) exposures in which the Dutch Poisons Information Center (DPIC) was consulted. Measurements Overall NPS incidence rate was the primary outcome. Numbers and specific categories of NPS were also studied. Changes in NPS incidence rates over time were analyzed using Poisson regression analyses [year effect expressed as incidence rate ratios (IRR)]. Findings From 2013 to 2017, NPS were involved in 1892 forensic samples, 6316 consumer samples and 481 poisons center exposures. In 2013, NPS incidence rates were 2.5, 7 and 4% versus 3, 11 and 11% in 2017, respectively, in the NFI, DIMS and DPIC samples/exposures. NPS incidence rates increased significantly in consumer samples between 2013 and 2016 [IRR=1.23; 95% confidence interval (CI) = 1.18, 1.29] and in poisons center exposures between 2013 and 2017 (IRR = 1.19; 95% CI = 1.06, 1.35), while the trend in forensic samples appeared more stable. Phenethylamines were the largest class and were detected in 58, 80 and 63% of NFI, DIMS and DPIC samples/exposures, respectively. Detected phenethylamines mainly involved 4-fluoroamphetamine and 2C-x derivatives. The second largest class were cathinones, which were detected in 21, 11 and 16% of NFI, DIMS and DPIC samples/exposures, respectively. Conclusions Analysis of forensic drug samples, consumer drug samples and exposures reported to poison centers from 2013 to 2017 shows the constant presence of new psychoactive substances on the Dutch drug market and its use by the Dutch population. The two largest classes present in the Netherlands were phenethylamines and cathinones.