Impact of prolonged cannabinoid excretion in chronic daily cannabis smokers blood on per se drugged driving laws.
Cannabis is the illicit drug most frequently reported with impaired driving and motor vehicle accidents. Some per se laws make it illegal to drive with any amount of drug in the body, while others establish blood, saliva, or urine concentrations above which it is illegal to drive. The persistence of Δ(9)-tetrahydrocannabinol (THC) in chronic daily cannabis smokers blood is unknown. Thirty male chronic daily cannabis smokers resided on a secure research unit for up to 33 days, with daily blood collection. Samples were processed in an ice bath during sample preparation to minimize cannabinoid adsorption onto precipitant material. We quantified THC by 2-dimensional GC-MS. Of the 30 participants, 27 were THC-positive on admission, with a median (range) concentration of 1.4 μgL (0.3-6.3). THC decreased gradually only 1 of 11 participants was negative at 26 days, 2 of 5 remained THC-positive (0.3 μgL) for 30 days, and 5.0% of participants had THC ≥ 1.0 μgL for 12 days. Median 11-hydroxy-THC concentrations were 1.1 μgL on admission, with no results ≥ 1.0 μgL 24 h later. 11-Nor-9-carboxy-THC (THCCOOH) detection rates were 96.7% on admission, decreasing slowly to 95.7% and 85.7% on days 8 and 22, respectively 4 of 5 participants remained THCCOOH positive (0.6-2.7 μgL) after 30 days, and 1 remained positive on discharge at 33 days. Cannabinoids can be detected in blood of chronic daily cannabis smokers during a month of sustained abstinence. This is consistent with the time course of persisting neurocognitive impairment reported in recent studies.