ADH	alcohol dehydrogenase
ADME	absorption, distribution, metabolism, and excretion (in this review, the fourth process is treated as clearance-like removal, since in vitro skin models have no excretory function)
AHT	4-amino-2-hydroxytoluene
AMT	total cumulative amount permeated
BCRP	breast cancer resistance protein
CBM	cutaneous biodistribution method
COMT	catechol-O-methyltransferase
CRS	confocal Raman spectroscopy
CYP	cytochrome P450
dOFM	dermal open-flow microperfusion
EFSA	European Food Safety Authority
EHS	ex vivo human skin
EMA	European Medicines Agency
ER	electrical resistance
FDA	U.S. Food and Drug Administration
FMO	flavin-containing monooxygenase
FTSE	full-thickness skin equivalent
GelMA	gelatin methacryloyl
GST	glutathione S-transferase
HPLC	high-performance liquid chromatography
IVIVE	in vitro–in vivo extrapolation
IVPT	in vitro permeation testing
IVRT	in vitro release testing
LC–MS	liquid chromatography–mass spectrometry
LSE	living skin equivalent
MALDI	matrix-assisted laser desorption/ionization
MIVO	multi-in-vitro-organ (microphysiological platform)
MPS	microphysiological system
MRP	multidrug resistance-associated protein
MSI	mass spectrometry imaging
NAT	N-acetyltransferase
OECD	Organisation for Economic Co-operation and Development
PBPK	physiologically based pharmacokinetic
PDMS	poly(dimethylsiloxane)
P-gp	P-glycoprotein
RHE	reconstructed human epidermis
SC	stratum corneum
TEWL	transepidermal water loss
TG	Test Guideline
UGT	UDP-glucuronosyltransferase
UHPLC–MS/MS	ultra-high-performance liquid chromatography–tandem mass spectrometry
XME	xenobiotic-metabolizing enzyme
A	exposed diffusion area
Cd	dissolved donor concentration in contact with the barrier
Cin, Cout	compound concentration in the inlet and outlet perfusate
CLapp	apparent concentration-normalized clearance
Cref	concentration in the compartment from which the compound is removed
Deff	effective diffusion coefficient
Jmax	maximum flux
Jpeak	peak flux under finite-dose conditions
Jss	steady-state flux
Kp	apparent permeability coefficient
Q(t)	cumulative amount permeated per unit area
Qf	volumetric flow rate
Sv	saturation solubility of the compound in the applied vehicle
tlag	lag time
tpeak	time of peak flux