In recent years, drug testing or drug screening has become an integral part of a job application, in the sports field, or in the investigation of criminals.
It plays a significant role in the judicial system. With a drug test patch, it’s possible to trace a range of drugs like marijuana, cocaine, LSD, or heroin in the system depending upon their time of clearance from the body.
Some amount of drug or its breakdown products will be eliminated via skin in the form of sweat. In this regard, a drug test patch is an alternate technique to detect traces of drugs in the system, in place of the usual traditional methods like a blood test or urine test.
Drug test patch or sweat test patch is a relatively recent development in the forensic field. Although the primary use of sweat test patches was to monitor people on probation, it is now becoming increasingly popular among employers who use it to screen job applicants and employees for use of drugs.
Table of Contents
- What is a Drug Test Patch?
- How Do Sweat Patches Work?
- Drug Test Patch vs. Urine Test
- Disadvantages of Drug Test Patch
- Can a Drug Test Patch Cause False Positive?
- Can Lidocaine Patches Cause a Positive Drug Test?
What is a Drug Test Patch?
A drug test patch is a continuous monitoring device used to detect traces of marijuana or any other type of drug, weeds, or cannabis in the body. It is designed in such a way that it can provide evidence of whether the drugs are consumed for a prolonged period or not.
The person undergoing the test has to wear the patch 24hrs a day. This is to ensure that a sufficient amount of sweat gets collected in the patch and will give away better results.
Sometimes the patch has to be kept for several days until the sweat is cleared of the drugs. Whenever the person consumes drugs, a considerable amount of it will be excreted through sweat. And it will be collected in the patch which can be analyzed later in the laboratory.
This is the reason it is also known as a sweat test patch. It was approved by the FDA as a collection device in 1990 to detect traces of opium, cocaine, marijuana, and other drugs or weeds.
How Do Sweat Patches Work?
Sweat patches are made up of an absorbent pad which is attached to the skin of the person undergoing the test, usually on the arm. It is secured to the skin with the help of an adhesive film that resembles a Band-Aid.
The inner surface of the patch has an absorbent pad that absorbs sweat. In the testing center, the patch will be fixed to the individual’s arm. Once fixed it cannot be reattached after removing it. And each patch has a unique identification number which has been documented by the testing center. Hence any attempt to remove it and reattach some other patch will give away the fabrication.
The sweat deposits from the wearer’s skin get collected in the patch after it is worn for up to 14 days. Once 99% of the sweat evaporates as water, it leaves behind the chemical excretions on the patch.
Sweat patches detect alcohol, cocaine, heroin, etc. with accuracy. Hence they can be used as a comprehensive drug test.
While wearing the patch if the person consumes drugs at any point, the drug or its metabolite will be detected on the patch. This is after the patch is removed for forensic testing.
Initially, the patches used to cause skin irritation, alter the pH of the skin or colonize skin bacteria, but with the invention of newer, technically evolved patches like Pharm-Check patches these problems have been resolved. These new patches consist of a transparent film that allows oxygen or CO2 to diffuse but traps the traces of dug that is excreted through sweat.
Drug Test Patch vs. Urine Test
Although urine test is a traditionally employed method for drug testing, drug test patch has proven to be a better choice for the following reasons:
Longer Testing Window
In comparison to a urine test, a drug test patch has the advantage of a large detection period. Urine test involves strips which give off immediate results. If fast clearing drugs are used by a person they will not be detected by a urine test. But the drug test patches can be used for a longer duration.
It will continuously absorb and collect the sweat which can be analyzed at the end of one or two weeks and can be used as a piece of evidence. Some of the most commonly used drugs like marijuana, LSD, and cocaine remain in the system generally for about 5 to 6 days. In such cases, a traditional method of urine test has to be conducted repeatedly for several days. But the sweat patch test gives the result in a single test because of its long testing window. The court system is also in favor of these test patches because of the same reason.
In sweat patches, fear of contamination is less likely once it is attached, as the outer membrane of the patch is not permeable to infective or other materials.
Application of sweat test patches is easier and quicker. Unlike the urine test where urine has to be collected and has to be analyzed using the strips, attaching the test patches is more hygienic. However, if the patch test results are positive then it has to be further confirmed by a urine test.
Incidences of false-negative reports are less in drug test patches. Whereas in urine tests it is comparatively more when home testing kits or workplace kits are used. In drug test patches, false negativity is usually because of the patches picking up residues from past used drugs.
Drug test patch provides better results than urine test because it can detect the consumed drug as well as its metabolite i.e. the product of metabolism of the parent drug. Whereas urine tests can reveal only the metabolite. So if the person consumes the drug occasionally, a urine test cannot capture the drug because it is already metabolized.
Sweat patches provide a reliable source of evidence because once attached they cannot be removed or changed as they have a unique identification number. Whereas, urine test results can be easily manipulated.
Disadvantages of Drug Test Patch
While there are many advantages of sweat patches as an effective drug testing method, it is not free of flaws.
Sometimes contamination may result in a false positive report.
Reported drawbacks of sweat test patch include risk of environmental contamination of the patch before its attachment or after removal of the patch. Even the presence of secondhand marijuana smoke is sometimes detected as a positive test result.
Contamination from Within
This can occur when a person has drug residue on the skin before the application of the sweat patch. This is an occurrence that happens when the alcohol rub doesn’t completely remove the residue.
Another thing that happens with long-term drug users is the false positive that happens through skin storage. Here the patch gives out drug traces while wearing the patch. It gives the impression that the drug was consumed recently when in reality it was not.
Sometimes improper adherence to the patch can also cause problems. Accidental fall off or removal of the patch as a result of too much rubbing of the arm also may hamper the results.
Limits to Use
If a person is excessively hairy or has abrasions on the skin, the sweat patch cannot be used.
Additionally, a patch test is far more expensive than a urine test.
Can a Drug Test Patch Cause False Positive?
The results for drug tests by urine test may come negative even if sweat patch test results are positive. This is because the detection period of the drugs in urine is very short. But sweat test patch results can also be falsely positive if the sweat is stored for a long time.
This could be mainly due to environmental contamination although there are other factors which could contribute to a false positive result in a drug test patch. Certain food substances like poppy seeds can give a positive report for opium.
Likewise, certain medicinal drugs can also trigger false-positive results which most of the drug monitors or doctors are not aware of.
Some of the Over-The-Counter (OTC) medications also deliver a false-positive result. As well as some antidepressants or medications for cold can trigger false-positives for amphetamines. It is found that HIV medications can lead to false positives for marijuana.
Can Lidocaine Patches Cause a Positive Drug Test?
Known under the brand name called Lidoderm, Lidocaine is a local anesthetic.
It is available for use only under prescription. Unlike other anesthetics which is administered using an oral pill or through an injection, this medication is infused into a patch that is attached to the skin.
Lidocaine patch causes a temporary loss of sensation in the area where the patch is applied. It is used to lessen chronic back or neck pain by blocking the nerve signals.
The medication enters the body through the skin and temporarily treats symptoms of nerve pain.
People who have tested positive for a drug test have claimed that Lidocaine patches have caused false-positive results.
Lidocaine gets metabolized quickly by the liver into several metabolites and is mainly excreted by the kidneys.
Although it is not completely known if Lidocaine is metabolized in the skin, studies have found no evidence to the claims that Lidocaine patches cause false-positive results.
Drug test patch has almost an equal amount of pros and cons.
Some of the obvious advantages like accuracy, hygiene, resistance to tampering make it a clear winner as compared to the traditional method of urine testing.
However, its disadvantages like prone to environmental contamination, false-positive due to skin storage, etc., cannot be ignored either. Furthermore, it is expensive compared to other tests.
Some test courts accept the drug test patch result as the final and some don’t. Hence its overall acceptance rate is yet to be determined.
However many companies have started using drug test patches as a type of drug screening method. So to be on the safer side, it’s better to be aware of the pros and cons of the drug test patch.