Four-year evaluation of drug-impaired driving drug concentrations.

Drug-impaired driving is a significant public health and safety concern in the USA. To help assess current patterns of drug use in drivers, we evaluated 4 years of drug positivity in a large cohort of suspected impaired drivers. Samples collected between January 2017 and December 2020 were tested via a method compliant with the National Safety Council's Alcohol, Drugs, and Impairment Division's Tier I scope of recommended drugs. In 2017, NMS Labs received 17 346 driving under the influence of drugs cases, 17 471 in 2018, 19 050 in 2019, and 16 539 in 2020. The most common drug class detected was cannabinoids in ∼50% of the cases each year. The most common drugs detected over the 4 years were delta-9 tetrahydrocannabinol (delta-9 THC), ethanol, amphetamine/methamphetamine, fentanyl, and alprazolam. Delta-9 THC increased in positivity over the study, having been identified in 45% of cases in 2017, 46% in 2018, 46% in 2019, and 49% in 2020. Ethanol was found in 59% of cases in 2017, 59% in 2018, 61% in 2019, and 53% in 2020. Delta-9 THC and ethanol were the most common drug combination, found together in ∼19% of the cases every year of the study. Statistically significant increases in the average concentration of the following drugs were observed: fentanyl (5.7 ng/mL in 2017 to 9.6 ng/mL in 2020), methamphetamine (301 ng/mL in 2017 to 381 ng/mL in 2020), and delta-9-THC (6.4 ng/mL in 2017 to 7.3 ng/mL in 2020). Other findings included increases in the maximum reported concentrations between 2017 and 2020 for amphetamine (1400 to 2700 ng/mL), methamphetamine (5550 to 13 000 ng/mL), and fentanyl (56 to 310 ng/mL). Statistically significant concentration decreases were noted for several central nervous system depressants, notably prescription benzodiazepines, and several prescription narcotic analgesics.