Urinalysis is one of the most reliable methods of testing drugs in the body of any individual. The pharmacokinetic profile of most of the drugs of abuse is such that after administration, they are metabolized in the GI mucosa and mainly in the liver and excreted in urine. Sometimes the drugs bypass the first pass metabolism and excrete unchanged in urine. This is the reason why drug detection in urine is widely followed over other methods.
But not all drugs can be detected at the same time. There is always a time interval between the administration of the drug and the time when the drug can be detected in urine. The drug detection period is almost nil for blood and saliva as the drugs circulate in the body only these two medium constantly. It would take several days to weeks and sometimes even months for the drugs to appear in the hair follicle and in the sweat. So before you proceed on to do any drugs test on yourself or your kids or employees or the armed forces, you must have a good knowledge about the drug detection period in the various systems in the body. For instance if any of your employee has consumed a drug just a few minutes back and you want to confirm it, then doing a urine drug test wont be of any use. Blood test would be more reliable in this case.
Another important factor to be considered in drug detection is the cut off concentration. Any drug consumed can be detected only if the drug attains a minimum concentration in the sample tested. This means that drug detection can be useful only if the drug is consumed chronically and has a cumulative effect. The SAMHSA has devised a drug detection table that enumerates the minimum cut off concentrations for the various drugs of abuse and the detection periods for various drugs in different samples.
So before you plan to test your employees for drug abuse, know the drug detection time urine. Sometimes in spite of having a good kit and a good methodology, you may miss it sometimes due to the presence of adulterants.
So when you talk about drug detection times, then you must also rule out the possibility of the use of adulterants. One of novel ways of combating this issue is by doing a random and surprise drug testing.