General
In the light of the serious consequences for the individual, and liabilities
which can be incurred in the event of a positive or incorrect test result,
Simpson et al1 discussed the need for established procedures covering storage,
chain of custody, confirmation of results and appropriate legal standards for
‘library’ matching of spectra from unknown substances (e.g. designer drugs)
requiring identification.
Most blood and urine tests for the presence of cannabinoids differ from
alcohol test results as these measure inactive metabolites of cannabis, and not
the active drug itself. Alcohol produces clear dose-related impairment as
measured by breath, blood or urine tests. The presence of cannabinoids in
urine merely signifies that the person had used or been exposed to cannabis at
some point prior to the test2.
Cannabis Pharmacokinetics
In the light of the serious consequences for the individual, and liabilities
which can be incurred in the event of a positive or incorrect test result,
Simpson et al1 discussed the need for established procedures covering storage,
chain of custody, confirmation of results and appropriate legal standards for
‘library’ matching of spectra from unknown substances (e.g. designer drugs)
requiring identification.
Most blood and urine tests for the presence of cannabinoids differ from
alcohol test results as these measure inactive metabolites of cannabis, and not
the active drug itself. Alcohol produces clear dose-related impairment as
measured by breath, blood or urine tests. The presence of cannabinoids in
urine merely signifies that the person had used or been exposed to cannabis at
some point prior to the test2.
Cannabis Pharmacokinetics
Pharmacokinetics is the study of the time course of how drugs are distributed
in the body, how long the effects last and how such effects relate to drug tests.
in the body, how long the effects last and how such effects relate to drug tests.
The major problem with measurement of metabolites is the very long
detection times, owing the the rapid deposition of cannabinoids in inert fatty
tissue following administration. Johannson et al3 reported that total amount of
THC metabolites and the levels of delta THC-acid could be followed up to 25
days after abstinence using EMIT cannabinoid assay and HPLC.
detection times, owing the the rapid deposition of cannabinoids in inert fatty
tissue following administration. Johannson et al3 reported that total amount of
THC metabolites and the levels of delta THC-acid could be followed up to 25
days after abstinence using EMIT cannabinoid assay and HPLC.
The residual level of THC in the bloodstream occurs when THC is released
from the adipose (fatty) tissues, where it is deposited shortly after smoking.
THC is also converted to its inert acid form within minutes of ingestion4. The
half-life of THC in fatty tissue is approximately 8 days56. There is little
evidence that clearance rates for THC differ significantly between naive and
experienced cannabis users.
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THC is also converted to its inert acid form within minutes of ingestion4. The
half-life of THC in fatty tissue is approximately 8 days56. There is little
evidence that clearance rates for THC differ significantly between naive and
experienced cannabis users.
