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On the surface, there are at least two questions that are posed when dealing with the issue of marijuana exposure. The first relates to whether or not a person has smoked marijuana, and the second relates to whether or not that person was impaired at a specific point in time. Screening tests on urine can provide information to past exposure, but these tests do not necessarily differentiate between exposure to second hand smoke and actually smoking marijuana. Quantification of marijuana, delta-9-tetrahydrocannabinol (THC), and its major metabolite, 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (THC-COOH), using GC/MS (gas chromatography/mass spectroscopy) is critical to understanding the extent of exposure and the nature of the species being examined. This leads into answering the second question involving possible impairment. Impairment from smoking marijuana is short lived, but metabolites of marijuana (THC-COOH) remain in the body and are excreted over several days. The principal metabolite, tetrahydrocanabinol carboxylic acid (THC-COOH), however, is not psychoactive; consequently, it is not thought to cause behavioral impairment. A finding of THC-COOH in the urine, does reflect past use of marijuana, but that use may have been several days prior to the taking of the urine sample. In chronic marijuana users, the elimination half-life of this metabolite could be as long as 40 hours; whereas, in infrequent users it averages 33 hours. Dr. Parent has participated in several marijuana cases and has accumulated a significant database. Selected references are provided below.

Selected References

Ameri, A., The effects of cannabinoids on the brain. Progress in  Neurobiology, 58(4), 315-348 (1999).

Block, R. I., Farinpour, R. and Braverman, K., Acute effects of marijuana on cognition: relationships to chronic effects and smoking techniques. Pharmacology Biochemistry and Behavior, 43, 907-917 (1992).

Chait, L. D., Subjective and behavioral effects of marijuana the morning after smoking. Psychopharmacology, 100, 328-333 (1990).

Cirimele, V., Kintz, P. and Mangin, P., Testing human hair for cannabis. Forensic Science International, 70(1-3), 175-182 (1995).

Cone, E. J. and Huestis, M. A., Relating blood concentrations of tetrahydrocannabinol and metabolites to pharmacologic effects and time of marijuana usage. Therapeutic Drug Monitoring, 15(6), 527-532 (1993).

Cone, E. J., Johnson, R. E., Darwin, W. D., Yousefnejad, D., Mell, L. D., Paul, B. D. and Mitchell, J., Passive inhalation of marijuana smoke: urinalysis and room air levels of delta-9-tetrahydrocannabinol. Journal of Analytical Toxicology, 11(3), 89-96 (1987).

Fant, R. V., Heishman, S. J., Bunker, E. B. and Pickworth, W. B., Acute and residual effects of marijuana in humans. Pharmacology Biochemistry and Behavior, 60(4), 777-784 (1998).

Fraser, A. D. and Worth, D., Urinary excretion profiles of 11-nor-9-carboxy-Delta9-tetrahydrocannabinol. Study III. A Delta9-THC-COOH to creatinine ratio study. Forensic Science International, 137(2-3), 196-202 (2003).

Heishman, S. J., Huestis, M. A., Henningfield, J. E. and Cone, E. J., Acute and residual effects of marijuana: profiles of plasma THC levels, physiological, subjective, and performance measures. Pharmacology Biochemistry and Behavior, 37(3), 561-565 (1990).

Huestis, M. A., Mitchell, J. M. and Cone, E. J., Urinary excretion profiles of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol in humans after single smoked doses of marijuana. Journal of Analytical Toxicology, 20(6), 441-452 (1996).

Huestis, M. A., Henningfield, J. E. and Cone, E. J., Blood cannabinoids. I. Absorption of THC and formation of 11-OH-THC and THCCOOH during and after smoking marijuana. Journal of Analytical Toxicology, 16(5), 276-282 (1992).

Johansson, E. K., Hollister, L. E. and Halldin, M. M., Urinary elimination half-life of delta-1-tetrahydrocannabinol-7-oic acid in heavy marijuana users after smoking. National Institute of Drug Abuse Research Monograph, 95, 457-458 (1989).

Klonoff, H., Marijuana and driving in real-life situations. Science, 186, 317-324 (1974).

Lemberger, L., Crabtree, R. E. and Rowe, H. M., 11-hydroxy- 9 -tetrahydrocannabinol: pharmacology, disposition, and metabolism of a major metabolite of marihuana in man. Science, 177(43), 62-64 (1972).

Moskowitz, H., Marijuana and driving. Accident Analysis and Prevention, 17, 323-345 (1985).

Stracciari, A., Guarino, M., Crespi, C. and Pazzaglia, P., Transient amnesia triggered by acute marijuana intoxication. European Journal of Neurology, 6(4), 521-523 (1999).

Tomaszewski, C., Kirk, M., Bingham, E., Saltzman, B., Cook, R. and Kulig, K., Urine toxicology screens in drivers suspected of driving while impaired from drugs. Journal of Toxicology Clinical Toxicology, 34(1), 37-44 (1996).

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