Extended plasma cannabinoid excretion in chronic frequent cannabis smokers during sustained abstinence and correlation with psychomotor performance.
Cannabis smoking increases motor vehicle accident risk. Empirically defined cannabinoid detection windows are important to drugged driving legislation. Our aims were to establish plasma cannabinoid detection windows in frequent cannabis smokers and to determine if residual cannabinoid concentrations were correlated with psychomotor performance. Twenty-eight male chronic frequent cannabis smokers resided on a secure research unit for up to 33 days with daily blood collection. Plasma specimens were analyzed for Δ(9) -tetrahydrocannabinol (THC), 11-hydroxy-THC (11-OH-THC), and 11-nor-9-carboxy-THC (THCCOOH) by gas chromatography-mass spectrometry. Critical tracking and divided attention tasks were administered at baseline (after overnight stay to ensure lack of acute intoxication) and after 1, 2, and 3 weeks of cannabis abstinence. Twenty-seven of the twenty-eight participants were THC-positive at admission (median 4.2 µgL). THC concentrations significantly decreased 24 h after admission, but were still ≥2 µgL in 16 of the 28 participants 48 h after admission. THC was detected in 3 of 5 specimens on day 30. The last positive 11-OH-THC specimen was 15 days after admission. THCCOOH was measureable in 4 of 5 participants after 30 days of abstinence. Years of prior cannabis use significantly correlated with THC concentrations on admission, and days 7 and 14. Tracking error, evaluated by the Divided Attention Task, was the only evaluated psychomotor assessment significantly correlated with cannabinoid concentrations at baseline and day 8 (11-OH-THC only). Median THC was 0.3 µgL in 5 chronic frequent cannabis smokers plasma samples after 30 days of sustained abstinence. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.