Susceptibility of PharmChek(TM) Drugs of Abuse Patch to Environmental Contamination

It has been well documented that ingested drugs appear in sweat. A sweat collection patch marketed by PharmChem, Inc. as the PharmChek(TM) Drugs of Abuse patch was developed through the joining of a non-occlusive membrane with a collection pad for use in drug detection. Sweat collection devices sandwich an absorbent pad between the skin and an outer membrane using a tamper-evident adhesive backing on the membrane. The cleansing of the skin prior to application of the patch aids in reducing the potential for bacterial growth and skin contamination. This patch is perceived by the criminal justice system as having wide application due to its user friendliness, non-invasiveness, easily observed placement and removal, detectable adulteration attempts, long drug-use detection interval of approximately 1 week while being worn, and the potential to identify unique metabolites. However, there have been questions regarding the reliability of results from the sweat patch due to external contamination from without, or outside the patch (CFWO) or from the prior presence of drugs on the exterior of the skin, not removed by the cleaning process (external contamination from within, under the patch- CFWI). This paper explored how these variables affect the reliability in detecting the use of drugs. Findings indicated that with the current design of the sweat patch problems with CFWO and CFWI could occur. A recommendation was presented to redesign the patch with an air gap to reduce the CFWO. Saving the swabs used for cleansing the skin (with possible inclusion of mild acid in the isopropanol) for testing can improve interpretations. In addition, following up on an individual who denies drug use with frequent urine tests will assist in improving reliability and respond to CFWO and CFWI. Continued research on sweat patch tests is recommended. Figures and references