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Kidwell DA, Smith FP. 
“Susceptibility of PharmChek Drugs of Abuse Patch to Environmental Contamination”. 
Naval Research Laboratory. 1999 November 3.
Chemistry Division, Code 6177, US Naval Research Laboratory, Washington, DC 20375,

The key component of the PharmChek sweat patch, the membrane, has been tested for the passage of externally applied materials. Drugs in the uncharged state rapidly penetrated the membrane but charged species were greatly slowed. In basic media, detectable concentrations of cocaine, methamphetamine, and heroin were observed at the earliest collection time (ca. 30 s), after drugs were placed on the outside of the membrane. Drug concentrations increased over the 2 h time course, when amounts detected (1710 ng cocaine, 1060 ng methamphetamine, 550 ng heroin per pad at 2 h) represented 5-17% of the drug deposited on the surface of the sweat patch.Drugs externally applied to human skin were shown to bind readily. Drugs deposited on the skin of drug-free volunteers several days prior to application of the sweat patch were not completely removed by normal hygiene or the cleaning procedures recommended before application of the sweat patch. Even 6 days of normal hygiene did not remove all drugs from externally contaminated skin and positive sweat patches resulted. A mechanism for passage of drugs through the sweat patch membrane, a mechanism for retention of drugs on skin, and a redesign of the sweat patch and modification of its use to reduce external contamination are proposed. Appropriate care should be taken in the interpretation of positive results from a sweat patch test until more research is conducted. (This work was partially supported by the Office of National Drug Control Policy through the U.S. Army Electronic Proving Ground and the DoD Counterdrug Technology Development Program at the Naval Surface Warfare Center. The opinions expressed in this paper are those of the authors and do not necessarily reflect the views of the Department of theNavy or the U.S. Government.)
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