CANNABIS. The cannabis constituent that produces the high is called Delta-9-tetrahydrocannabinol (Delta-9-THC, widely known as THC.)
Delta-9-THC enters the bloodstream rapidly after smoking (in minutes) or more slowly when ingested orally (20 minutes to 1.5 hours). It is rapidly metabolised into inert molecules known as metabolites. These chemicals also have the word Tetrahydrocannabinol in them and are called THC, which can be quite confusing.
Delta-9-THC is detectable in the blood for a few hours, but none of this active chemical is found in the urine or stored in the fatty tissues such as the liver and brain.
What is frequently described as THC's lingering in the body fluids and organs are metabolites of Delta-9-THC, the inert substances that the body disposes of in the urine and excrement, in much the same way as it disposes with Vitamin A. It is these that are detected in the body organs and urine, long after the effects of Delta-9-THC have worn off.
These metabolites can linger more than 90 days in some cases. For occasional users, an average of 13 days was recorded. Some people had metabolites detectable for just three days; others found the substances still in the urine after up to 29 days.
But a positive body fluid or hair test for cannabis does not mean that the person was under the influence of the substance, or impaired in any way at the time the specimen was collected. All it tells the tester is that the person may or may not have ingested cannabis in the recent past.

COCAINE is rapidly absorbed after smoking with the maximum plasma concentration occurring in 5 minutes. After snorting or sniffing maximum concentrations are reached in 30 to 40 minutes. Cocaine is metabolised extensively with only 1% being excreted unchanged in the urine. The major metabolite -Benzoylecgonine - can be detected by an immunoassay test for approximately 48 hours. Again, a drug test cannot show the level of impairment at the time the test was taken.

AMPHETAMINES are metabolised and the drug will appear in the urine. Unchanged amphetamines have been detected in the urine up to 29 hours after a single dose of 5 mg. A positive amphetamine analysis indicates the use of amphetamine 24 to 48 hours previously. Again, it cannot show the level of impairment at the time the test was taken.

OPIATES including morphine, heroin, are rapidly absorbed after oral ingestion, with peak plasma levels occurring about 15 to 60 minutes after the drug has been taken. After injection it peaks in 15 minutes. The principal metabolite for detection is morphine-3, glucronide, which can be detected in the urine for around 48 hours. Again, it cannot show the level of impairment at the time the test was taken.

HEROIN has a similar pattern of metabolisation and excretion to morphine, and a typical test will show a positive result between two and four days after use. Again, it cannot show the level of impairment at the time the test was taken.

LYSERGIC ACID DIETHYLAMIDE (LSD) has its effect within minutes after use but can last for 12 hours. LSD is rapidly metabolised and only a very small portion of the dose is excreted unchanged in the urine. LSD itself, however, can be detected up to 30 hours after use and the metabolites can be detected for periods of up to 72 hours. Again, it cannot show the level of impairment at the time the test was taken.

Complied by Don Barnard