Sweat testing in addicts under methadone treatment: an Italian experience

In the last years the interest in monitoring drug exposure with human sweat as alternative biological fluid, is increasing. Sweat collection is convenient, less invasive and difficult to adulterate compared to traditional specimens. The objective of this study was to determine the excretion profile of methadone and other drugs into human sweat. Pharmscope sweat patches (Medical Europe Diagnostic, Madrid, Spain) were used on heroin abusers under methadone treatment. Sweat patches were applied to 10 heroin addicts and 3 drug free volunteers admitted into the study. Sweat patches were worn for about 1 week; urine, saliva and hair samples were collected at the time of the removal of patches. After the extraction, sweat eluates were directly analyzed by GC/MS for the presence of nicotine, cotinine, caffeine, methadone, EDDP and cocaine. The extracts were subsequently derivatized to detect benzoylecgonine, ecgonine methyl ester, morphine, codeine and 6-acetylmorphine. No false positive results were obtained on the drug free samples. All the patches showed positive results for methadone. Cocaine was detected in two cases. Mainly the parent drug was identified rather than the metabolites. The results obtained show the usefulness of sweat as complementary specimen to saliva and urine providing a longer detection window. Moreover, sweat testing offers the advantage of being a non-invasive means of obtaining information about drug exposure.