Skin Permeability Coefficient
Evaluate a caller-calibrated linear log10 skin permeability model from logKow and molecular weight; model coefficients, applicability and chemical ionization are external.
Description
Evaluate a supplied log-permeability QSAR using log Kow, molecular weight, and calibration coefficients.
A quantitative structure–activity relationship, or QSAR, relates measured properties to an endpoint through a calibrated equation. Skin-permeability models can use molecular size and octanol–water partitioning as predictors of transport through skin. Their calibration and applicability domain determine interpretation.1
This tool evaluates a linear model for log10 of permeability and converts it back to cm/hour. You supply all three coefficients; the example values are not hidden defaults. The molecular-weight convention, commonly g/mol numerically, must match the calibration, and logKow is a dimensionless base-10 logarithm.
When to use Skin Permeability Coefficient
Use it to reproduce a documented calibrated equation or compare predictions under explicit coefficient sets.
How to use Skin Permeability Coefficient and understand its results
- Enter finite logKow and positive molecularWeight using the units and property definitions expected by the calibration.
- Enter finite intercept, logKowCoefficient, and molecularWeightCoefficient fitted for log10 permeability in cm/hour, then run the tool.
- Read log10PermeabilityCmPerHour and permeabilityCmPerHour together and compare the inputs with the model’s documented applicability domain.
log10 Kp = intercept + logKowCoefficient × logKow + molecularWeightCoefficient × molecularWeight; Kp = 10^(log10 Kp) The implementation applies the coefficients directly and performs no fitting, unit conversion, or property lookup.
{
"input": {
"logKow": 2,
"molecularWeight": 100,
"intercept": -2.72,
"logKowCoefficient": 0.71,
"molecularWeightCoefficient": -0.0061
},
"output": {
"log10PermeabilityCmPerHour": -1.9100000000000001,
"permeabilityCmPerHour": 0.012302687708123811
}
}Negative logKow and zero or negative coefficients are allowed. With both predictor coefficients zero, permeability depends only on the intercept. Molecular weight zero is rejected; extremely large log predictions can overflow, while very negative predictions can underflow to zero.
Limitations and assumptions
The calculator does not determine ionization, formulation effects, skin integrity, temperature, calibration quality, or confidence intervals. A finite result does not demonstrate model applicability.
A permeability coefficient is not an absorbed dose or absorption fraction. Estimating flux or dose additionally requires a suitable transport and exposure model.
Alternative or Complementary methods
Use a dermal contact-dose calculation when contacting mass and absorption fraction have already been established. Distance-based analogue prediction is another explicit model and requires its own evidence and descriptor scaling.
References
-
Predicting skin permeability (Potts and Guy, 1992) — Pharmaceutical Research
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