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XXXV TIAFT Annual Meeting Poster Presentations
KINETICS OF 11-NOR-δ-9-THC-CARBOXYLIC ACID (THC-COOH) IN URINE

Dalén P., Villén T., Stahle L.

Division of Clinical Pharmacology, Department of Medical Laboratory Sciences and Technology, Karolinska Institute, Huddinge University Hospital, SE-14186 Huddinge, Sweden

The aim of this study was to investigate the kinetics in the urine of THC-COOH in patients monitored in routine health care.
Methods. Because dosage, time of intake and urine productione rates are unknown in the abuse situation, a novel approach is used to make identification possible of the pharmacokinetic "state" of the abuser. Eighteen subjects (10 from narcotic care, 8 from company health care) for whom several urine samples have been obtained were included in the analysis. For cannabis screening FPIA (Flourescence-Polarization-Immuno-Assay) was used and for verification gaschromatography-masspectrometry was used. Cut-off limit for screening was 25 ng/ml and, for verification, 10 ng/ml. The apparent half-life (t1/2) for 11-nor-δ-9-thc-carboxylic acid (THC-COOH) was calculated by least-squares linear regression analysis of log-urine concentration versus time curves from the terminal linear part of the curve for both the initial phase and the terminal phase. The initial phase was defined as the period immediately after an increase in concentration or as the first part in a two-compartment situation. All calculations were made on urine THC-COOH and on THC-COOH concentration divided by the creatinine concentration (THC-COOH/CR).
Results. In five cases data are abundant and fit a two compartment model. For these cases the t1/2 are 57 ± 39 hours for the initial phase and 333 ± 111 hours for the terminal phase. In seven cases where the data were judged to be "initial" because a recent increase in THC-COOH/CR could be shown, the half-life was 71 ± 41 hours. In the six cases of "terminal phase" the half-life was 195 ± 54 hours. In one case a two-phase model was considered appropriate despite only 3 samples available and the half-lives were 65 and 494 hours. Analysis of THC-COOH data were not a reliable due to large concentration fluctuations caused by variation in urine CR concentration.
Conclusions. The kinetics of THC-COOH/CR can be divided into an initial phase with a half-life around 66 hours and a terminal phase of around 260 hours (all data included). These preliminary observations suggest that the kinetics of THC-COOH/CR can be used to evaluate if cannabis intake has been recent or not.

  Abstract 077

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