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

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.