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Drugs of different chemical structures leave (or are excreted) from the body by different routes after they have been absorbed and distributed.
In humans, the major route that drugs take to leave the body is through urine. Drugs, once in the bloodstream, travel to the kidneys, where they are absorbed and filtered and then the remaining or residual blood, while water and the substance travel to the bladder and then leave the body through urination.
What is the difference between urine concentrations of substances and blood concentrations of substances?
The differences between urine concentrations and blood concentrations of substances are determined by the following:
1. the chemical structure of the drug
2. the pH (relative acidity) of the urine - which can vary chemically by disease conditions after administering certain drugs
3. the absorption process by the kidneys, which varies among individuals
4. the time that passes between formation of urine concentration stored in the bladder and emptying of the bladder
What is the best way to test for marijuana?
THC (delta 9--tetrahydrocannabinol) is the active ingredient found in marijuana. THC is fat-soluble. When smoking marijuana, THC is distributed to various body organs, especially those with high amounts of fat tissues. Thus, THC is metabolized (or processed through the body) quite slowly. Therefore THC can remain in the body, being slowly released into the urine for several days or weeks - depending on how much an individual smokes, how often they smoke, the percentage of THC in the marijuana and the rate the individual metabolizes. Individuals with large amounts of fat (or obese) will eliminate THC even more slowly.
Testing for THC: urine (urinalysis) - a positive result may indicate either recent use or use that occurred several weeks earlier. In addition, because of the slow rate of elimination as well as other factors, a positive urine test for marijuana may have no relationship with the presence of THC in the blood. Peak blood levels of THC occur about 10 minutes after starting to smoke. Within 2 hours, blood levels generally fall to low levels but may be detectable for up to 12 hours.
Therefore, urine testing may be the best way to detect whether or not someone has used marijuana within a 2-4 week period.
What about detecting drugs other than marijuana using urine testing?
Most other drugs of abuse, including cocaine, heroin (opiate family), phencyclidine (angel dust), and amphetamines (speed), because of their rates of absorption and metabolism (processing them through the body), can be detected in urine samples up to 72 hours after use.
Alcohol is water-soluble, so it passes through the body more rapidly than most other substances of abuse. Therefore, using urine testing, blood testing, or a breathalyzer to detect alcohol levels needs to be performed within 24 hours of the start of drinking or else elimination of alcohol will cause a negative test result.
How do individuals attempt to hide or get rid of drugs (drug metabolites) in their body?
People have been known to attempt to hide the detection of their drug use, when asked to submit a sample for urine testing by the following:
How can someone successfully eliminate or clean the urine sample to avoid detection?
Using marijuana as an example (because it has the longest time that it can be detected in a urine sample), marijuana (THC) is absorbed in the fatty tissue and is slowly released into the bloodstream. So, the only successful way to avoid detection is to reduce or eliminate the fatty cells through exercise. Thus, elimination of THC from a person's urine sample takes time - as much as 30 days.
Can someone pass a drug test by diluting the sample?
Flushing or saturating the body with water or other fluids will dilute drug metabolites to produce negative results on drug tests, depending on an individual's metabolism.
Two situations can occur, however, where the attempt at diluting a sample will be detected by drug testing administrators.
1. Although most drug tests (urinalysis) measure PH levels in the urine - many laboratories also measure creatine levels. The creatine levels will show if the drug test has been diluted.
2a. Diluting a sample by drinking water will also produce a clear colored urine sample with virtually no yellow urine color. Most drug test administrators assume a clear colored sample is diluted.
2b. Some individuals add a B-vitamin to add the yellow color to the urine. That sometimes works in terms of adding color to the sample but creatine levels would ultimately prove dilution.
Can someone pass a drug test by using diuretics?
Diuretics will cause an individual to urinate more often.
Diuretics frequently used include the following:
Other products sold commercially as drug testing adulterants are the following:
How are drug tests contaminated to give false results?
Here are the common ways accuracy is affected when drug tests (urinalysis) are given:
1. Contamination of specimen or container
2. Quality of the laboratory
3. Type of tests used
4. Carelessness of the collection
5. Technician error in testing
Deliberate sabotage of samples for drug testing occurs by the following:
1. Placing chemical substances under fingernails to release into sample
2. Puncturing specimen container with a pin, allowing urine to leak out slowly during transport to lab
3. Adding soap from restroom dispensers to specimen
4. Replacing clean urine with contaminated sample
5. Scooping water from toilet to dilute sample
Type of Test | Sensitivity to Contamination | Availability |
---|---|---|
On-site test cups (immediate results) | Poor | Commercially sold at pharmacies & on the internet |
Toxicology Screen (TLC) in laboratory | Poor | Inexpensive, available in most labs |
Chemical Analysis (G C-ms) | Excellent | Expensive, available in most labs |
Immunoassay (RIA, EIA) | Good | Moderate cost, available in many labs, easily automated |
Drug | Tranquilizer | Detection Period |
---|---|---|
Amphetamine | Stimulant | 2-4 days |
Barbiturate | Sedative | 12 hours - 3 weeks |
Cocaine | Stimulant | 2-4 days |
Fentanyl | Narcotic (opioid) | less than 1 hour |
Heroin/Morphine | Narcotic (opioid) | 2-4 days |
Marijuana | Hallucinogen | 3 days to 1 month |
Methadone | Analgesic | 2-4 days |
PCP (Angel Dust) | Anesthetic | 1-30 days |
Benzodiazepine | Tranquilizer | Up to 1 week |
Disclaimer:
Statements made on this website are for educational and informational purpose only and are not meant or intended as a substitute for medical advice. Information and statements have not been evaluated by the US Food and Drug Administration and are not intended to diagnose, treat or prevent any disease or medical condition.
References:
Brands et al… (Editors), Drugs and Drug Abuse: A Reference Text,
Addiction Research Foundation (Toronto, Canada) 1998.
Julien, Robert, A Primer of Drug Action, Worth Publishers (NY) 2002.
Kalant, Corrigall, Hall, Smart, (Editors),
The Health Effects of Cannabis, Addiction Research Foundation (Toronto, Canada) 1999.
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