The process of drug testing in USA was initiated in the latter part of the 1980s. During this period, the employees of the federal government as well as those who are covered under the DOT regulations. The guidelines for drug testing have been developed and are controlled by SAMHSA i.e. Substance Abuse and Mental Health Services Administration. In the past, these guidelines used to be monitored by NIDA i.e. National Institute on Drug Abuse. As per DOT regulations, it is necessary that employees who are engaged in driving wherein public safety is important, such as in case of trains, buses, planes, trucks, etc. undergo drug testing. People who are engaged in occupations wherein they are required to deal with oil and gas also need to undergo drug testing. The guidelines specify testing for 5 different groups of drugs, which are:

1. Cannabinoids, including marijuana and hashish
2. Cocaine, including cocaine, benzoylecognine and cocaethylene
3. Amphetamines, including amphetamine, and methamphetamine
4. Opiates, including heroin, opium, codeine, and morphine
5. Phencyclidine i.e. PCP

Unfortunately, these guidelines do not include the group called Semi-synthetic opioids, which includes drugs that are currently the most abused drugs in USA. This category includes drugs such as oxycodone, oxymorphone, hydrocodone, hydromorphone, etc.
According to the SAMHSA/NIDA guidelines, employees are required to undergo lab testing for the NIDA-5, that is the above 5 categories of drugs. However, some labs also undertake testing for other drugs which have higher rates of abuse in the country. Tests for the abuse of pain killers such as Oxycodone, Oxymorphone, Hydrocodone, Hydromorphone, barbiturates and benzodiazepines like Valium, Xanax, Klonopin and Restoril are included in such testing. Laboratory tests can be used to test the presence of similar drugs like methamphetamine and ecstasy. If only ecstasy is detected in the sample while a considerable amount of methamphetamine is not present, the laboratory can either report the result as ‘Negative’ or ‘Positive for ecstasy’. The reporting of the result by the laboratory depends upon what drug the employee was to be tested for.
In the earlier part of the 90’s, GHB, that is Gamma-hydroxy-butyrate, testing was rarely undertaken. However, labs started performing this test on account of the rising rates of usage. Generally, GHB testing is not undertaken for employment purposes, but it is done when drug abuse or deliberately missing a drug test is suspected. Post mortem toxicology tests also include this. Testing for Ketamine or Special K depends upon the entity ordering the testing. Such testing is, however, rare. Many employers prefer to undertake only NIDA-5 testing for financial reasons. When the number of drugs tested increase, the cost of the test would also rise.
Usually testing for drugs like meperidine (Demerol), fentanyl, propoxyphene, and methadone is not done for employment screening purposes. However, when certain specific groups of people are to be tested, such as healthcare workers or drug rehab patients, such testing might be undertaken.
Testing is also not generally done for hallucination-inducing agents like mushrooms (psilocybin), LSD, and peyote (mescaline). However, the agents cannabis and PCP are tested.

Detection periods

LabCorp’s chart given below gives an idea of the approximate time that each type of drug would take to be reflected in the lab test. This period is called the detection period. This time depends upon a number of factors such as the quantity of the drug used, the frequency of use, age and health of the user, body weight, and pH in the urine. The detection period of metabolites might be different from their parent drug. For instance, when a person consumes cocaine or heroin, it can be detected only for a few hours after consumption. However, their metabolites can be found in the urine of the user for a number of days thereafter. For this reason, this chart incorporates the detection period of metabolites into that of their parent drugs. The longer time that is taken for the detection of metabolites is mentioned in the chart.
NOTE 1: Generally, the results of a saliva test or an oral fluid test would be similar to those of a blood test. However, there is one exception to this – THC. THC can be detected in oral fluid for up to 18-24 hours after consumption.
NOTE 2: For a drug to be reflected in the urine of the user, it would take a period of 6-8 hours. This is the time period that the drug takes to enter the system of the user and to form part of the urine. Hence, a urine test would not reflect drugs consumed immediately prior. In the same way, for a drug to be reflected in hair, a period of two weeks is needed, while in case of sweat, it is a week.

Drug Detection Periods

Substance	Urine	Hair	Blood
Alcohol	3-5 days via Ethyl Gluconoride(EtG) metabolite or 10-12 hours via traditional method		12 hours
Amphetamines (except meth)	1 to 2 days	up to 90 days	12 hours
Methamphetamine	2 to 4 days	up to 90 days	24 hours
Barbiturates (except phenobarbital)	2 to 3 days	up to 90 days	1 to 2 days
Phenobarbital	7 to 14 days	up to 90 days	4 to 7 days
Benzodiazepines	Therapeutic use: 3 days. Chronic use (over one year): 4 to 6 weeks	up to 90 days	6 to 48 hours
Cannabis	Single Use: 2 to 3 days Chronic Use: 3 to 5 days, sometime longer	up to 90 days	2 days
Cocaine	2 to 4 days	up to 90 days	24 hours
Codeine	2 days	up to 90 days	12 hours
Cotinine (a break-down product of nicotine)	2 to 4 days	up to 90 days	2 to 4 days
Morphine	2 days	up to 90 days	6 hours
Heroin	2 days	up to 90 days	6 hours
LSD	2 to 24 hours	Up to 3 days	0 to 3 hours
Methadone	3 days	Up to 30 days	24 hours
PCP	14 days; up to 30 days in chronic users	up to 90 days	24 hours