Athccooh

Figure 3.14

Structures of THC and selected THC metabolites

8b-OH-A9-THC

8b-OH-A9-THC

8a-OH-A9-THC

8a-OH-A9-THC

11-OH-A9-THC

11-OH-A9-THC

8b,11 -diOH-A9-THC

8b,11 -diOH-A9-THC

formed to 11-hydroxy-A9-THC (11-OH-THC), which is subsequently oxidized to 11-nor-A9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH). The major THC metabolite in urine is THC-COOH, which is present as both the free acid and its glucuronide conjugate (Williams and Moffat, 1980; Kanter et al., 1982b; Wall et al., 1983). Although the unconjugated THC-COOH is the "target analyte" for cannabinoids screening and confirmation, its glucuronide conjugate is present in considerably higher concentrations than the parent drug in urine and blood (Skopp and Potsch, 2002a, 2002b). Other metabolites found in urine (Figure 3.14) are 8-a-hydroxy-A9-THC, 8-b-hydroxy-A9-THC, 8-0,11-di-hydroxy-A9-THC, 11-hydroxy-A9-THC, and a group of acid metabolites.

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