Journal Article

Pharmacokinetic Properties of Δ<sup>9</sup>-Tetrahydrocannabinol in Serum and Oral Fluid

Gerold F. Kauert, Johannes G. Ramaekers, Erhard Schneider, Manfred R. Moeller and Stefan W. Toennes

in Journal of Analytical Toxicology

Volume 31, issue 5, pages 288-293
Published in print June 2007 | ISSN: 0146-4760
Published online June 2007 | e-ISSN: 1945-2403 | DOI:
Pharmacokinetic Properties of Δ9-Tetrahydrocannabinol in Serum and Oral Fluid

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In a study on the effects of smoked cannabis (18.2 ± 2.8 mg as low and 36.5 ± 5.6 mg as high dose) paired blood and oral fluid samples were collected from 10 study participants up to 6 h after smoking and analyzed for the cannabinoids Δ9-tetrahydrocannabinol (THC), 11-hydroxy-THC (THC-OH) and 11-nor-9-carboxy-THC (THCA) using gas chromatography-mass spectrometry. Highest concentrations in serum were 47.8 ± 35.0 and 79.1 ± 42.5 µg/L at the end of smoking (low and high dose, respectively) and decreased to less than 1 µg/L during 6 h with elimination half-lives of 1.4 ± 0.1 h calculated from 1 to 6 h, which is shorter than reported previously. The elimination half-lives of THC-OH (2.0 ± 0.3 h) and THCA (3.4 ± 0.9 h) were significantly higher. The THC concentrations in oral fluid were highest with 900 ± 589 and 1041 ± 652 µg/L (low and high dose, respectively) in the first sample collected at 0.25 h and decreased to 18 ± 12 µg/L over 6 h with elimination half-lives of 1.5 ± 0.6 h. The elimination half-life of THC in serum and oral fluid and between the two doses did not significantly differ. Oral fluid/serum ratios were 46 ± 27 and 36 ± 20 (low and high dose, respectively), which are higher than previously reported and might be based on sample collection and/or analytical issues. In conclusion, despite similar elimination rates of THC in serum and oral fluid, which appear incidental, the high differences in oral fluid/serum ratios are not a reliable basis for correlating THC concentrations in oral fluid and serum. The oral compartment and its kinetics for drugs, particularly THC, are not yet satisfactorily understood.

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Subjects: Medical Toxicology ; Toxicology (Non-medical)

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