Disposition of cocaine and its metabolites in human sweat after controlled cocaine administration

Clin Chem. 2005 Nov;51(11):2085-94. doi: 10.1373/clinchem.2005.054338. Epub 2005 Sep 15.


Background: Sweat testing is a noninvasive technique for monitoring drug exposure in treatment, criminal justice, and employment settings.

Methods: We evaluated cocaine excretion in 9 participants' sweat after they received 3 low doses (75 mg/70 kg) of cocaine HCl subcutaneously within 1 week and, 3 weeks later, 3 high doses (150 mg/70 kg). Six additional participants completed portions of the study. PharmChek sweat patches (n = 1390) were collected throughout a 3-week washout period, reflecting previously self-administered drugs, and during and after controlled dosing.

Results: Cocaine was the primary analyte detected with 24% of patches positive at the gas chromatography-mass spectrometry limit of quantification of 2.5 ng/patch and 7% of patches at the proposed Substance Abuse and Mental Health Services Administration cutoff of 25 ng/patch. Ecgonine methyl ester (EME) was detected more often and at generally higher concentrations than benzoylecgonine. In patches containing both metabolites, there was no statistically significant difference in the benzoylecgonine/EME ratio based on length of patch wear. During washout, 2 participants' weekly patches tested positive (> or =25 ng/patch) during the first week; one remained positive during week 2; and none were positive during week 3. Cocaine and EME were detectable within 2 h; benzoylecgonine was not detected until 4-8 h after low doses and slightly sooner after high doses. The majority of drug was excreted within 24 h. Over 70% of weekly patches worn during low doses were positive for cocaine (> or =25 ng/patch), increasing to 100% during high doses.

Conclusion: Sweat testing is an effective and reliable method of monitoring cocaine exposure.

Publication types

  • Clinical Trial
  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Cocaine / administration & dosage
  • Cocaine / analogs & derivatives
  • Cocaine / metabolism
  • Cocaine / pharmacokinetics*
  • Female
  • Humans
  • Male
  • Substance Abuse Detection*
  • Sweat / metabolism*


  • benzoylecgonine
  • Cocaine
  • ecgonine methyl ester