Elimination of Cannabis from the System
Metabolism is the major route for the elimination of THC from the body. As a result, only negligible amounts of THC are excreted in unchanged form; of an oral dose, about 15-30% of THC is excreted in urine with less than 0.05% of unchanged THC, and about 30-65% is excreted in feces with less than 5% as unchanged drug. Among the metabolites, 11-COOH-THC is a major one identified in both urine and faeces, in its native as well as in its glucuronidated form.
The half-life of THC and its metabolites is dependent on the detection method and can be several days. The slow elimination from the plasma could be explained by redistribution from peripheral tissues, such as adipose tissue, into the bloodstream. Following single dose administration, low levels of THC metabolites have been detected for more than 5 weeks in the urine and faeces.