FAQ: Drug Patch Testing

The drug patch is an absorbent pad fastened to the skin by 3M Tegaderm adhesive to secure it.  This is the same product used in hospitals to secure an IV or bandage.

The white absorption pad is covered by a polyurethane film, which protects it from the environment but allows the transfer of water vapour and gases from the body.  Drugs excreted from the body in sweat are trapped and retained in the absorbent pad.

The patch is a collection device designed to retain evidence of drug use for an extended period. It can detect use 24-48 hours before the application of the patch and during the wearing of the patch, or both.

For example: a patch worn for 7 days might be positive because of drug use on Day 1 or on Day 6 of the patch, or both.

Urine analysis for drugs represents a snapshot in time.

The drug patch, unlike urine testing, functions as a storage device. Drugs used 1-2 days before the patch is applied, while the patch is worn, and up to 24 hours prior to the removal of the patch are detected and stored in the patch.

Consequently, the drug patch is a constant monitoring device, which provides the drug patch with a longer detection window than urine testing.

Yes. As indicated above, the drug patch acts as a storage device and represents a much longer detection window than urine testing.

In addition, urine tests are subject to various forms of adulteration including but not limited to hydration, substitution and physical adulteration using products designed to affect the testing procedures.

No, not in the same sense that urine specimens can be adulterated. The sweat patch is a tamper evident device.  When the sweat patch is removed, epithelial skin cells stick to the adhesive and will prevent the re-application of the drug patch

Attempts to adulterate the drug patch will typically result in a visible discoloration of the white absorption pad and/or discoloration or deformation of the polyurethane covering.  Any tampering would be noted on the chain of custody document at the time of patch removal.

No. The drug patch is a storage device. So multiple drugs use while wearing the patch will result in increased drug levels in the patch. However as these are accumulative, the patch cannot distinguish multiple instances of drug use.

None.  Unlike urine specimens which can be diluted because of hydration/ flushing which may dilute the concentration of drugs in the urine, the consumption of large amounts of fluids does not decrease the drug concentrations in the drug patch.

The absorbent pad within the patch is protected from the environment by a layer of film composed of polyurethane coated with adhesive. The polyurethane film is a “semi-permeable membrane,” which allows the transfer of water vapor and gases while preventing outside contaminants from entering

With a positive patch result, it is not possible to determine exactly when the drug use took place, only that the drug use took place 24-48 hours before the application of the patch, during the wearing of the patch, or both.

It is possible to detect residual usage between multiple patch wear periods if drugs were consumed late in the first wear period and thus picked up early in the second patch wear period.

Allergic reactions are extremely rare. 3M, the maker of Tegaderm used in the manufacturing of the drug patch states that less than 1% of the population is allergic to Tegaderm.

Tegaderm is a hypoallergenic material used as a wound dressing to cover catheter and IV sites of individuals in hospitals, and widely used within the medical field.