Initial Development toward Non-Invasive Drug Monitoring via Untargeted Mass Spectrometric Analysis of Human Skin

Anal Chem. 2019 Jul 2;91(13):8062-8069. doi: 10.1021/acs.analchem.8b05854. Epub 2019 Jun 10.


Drug monitoring is crucial for providing accurate and effective care; however, current methods (e.g., blood draws) are inconvenient and unpleasant. We aim to develop a non-invasive method for the detection and monitoring of drugs via human skin. The initial development toward this aim required information about which drugs, taken orally, can be detected via the skin. Untargeted liquid chromatography-mass spectrometry (LC-MS) was used as it was unclear if drugs, known drug metabolites, or other transformation products were detectable. In accomplishing our aim, we analyzed samples obtained by swabbing the skin of 15 kidney transplant recipients in five locations (forehead, nasolabial area, axillary, backhand, and palm), bilaterally, on two different clinical visits. Untargeted LC-MS data were processed using molecular networking via the Global Natural Products Social Molecular Networking platform. Herein, we report the qualitative detection and location of drugs and drug metabolites. For example, escitalopram/citalopram and diphenhydramine, taken orally, were detected in forehead, nasolabial, and hand samples, whereas N-acetyl-sulfamethoxazole, a drug metabolite, was detected in axillary samples. In addition, chemicals associated with environmental exposure were also detected from the skin, which provides insight into the multifaceted chemical influences on our health. The proof-of-concept results presented support the finding that the LC-MS and data analysis methodology is currently capable of the qualitative assessment of the presence of drugs directly via human skin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Administration, Oral
  • Chromatography, Liquid / methods
  • Citalopram / administration & dosage
  • Citalopram / pharmacokinetics
  • Diphenhydramine / administration & dosage
  • Diphenhydramine / pharmacokinetics
  • Drug Monitoring / methods*
  • Humans
  • Mass Spectrometry / methods
  • Selective Serotonin Reuptake Inhibitors / administration & dosage
  • Selective Serotonin Reuptake Inhibitors / pharmacokinetics
  • Skin / metabolism*
  • Skin Absorption*
  • Sleep Aids, Pharmaceutical / administration & dosage
  • Sleep Aids, Pharmaceutical / pharmacokinetics


  • Serotonin Uptake Inhibitors
  • Sleep Aids, Pharmaceutical
  • Citalopram
  • Diphenhydramine