Dermal clearance model for epidermal bioavailability calculations.

Area of Science:

• Pharmacokinetics
• Computational Biology
• Dermatology

Background:

• Estimating dermal clearance of nonmetabolized solutes is crucial for understanding chemical exposure.
• Existing models may lack precision for diverse molecular sizes and binding characteristics.

Purpose of the Study:

• To develop a computational model for estimating dermal clearance in humans.
• To incorporate both blood capillary and lymphatic system contributions to solute transport.
• To improve predictions of tissue concentrations after dermal exposure.

Main Methods:

• Developed a computational model integrating slit theory for blood capillary permeability (10 nm and 50 nm slits).
• Incorporated lymphatic clearance data from human dermal and subcutaneous injections of (131)I-albumin.
• Fitted model parameters to experimental blood capillary permeability and lymphatic clearance data.

Main Results:

• The model differentiates clearance pathways: blood for small molecules, lymph for large molecules.
• Observed a crossover behavior around 29 kDa, aligning with reported values (e.g., 16 kDa).
• Model shows potential for improved tissue concentration estimates when combined with stratum corneum and binding models.

Conclusions:

• The developed computational model provides a framework for estimating dermal clearance of nonmetabolized solutes.
• The model highlights the distinct roles of blood capillaries and lymphatic systems in solute removal.
• This model offers enhanced predictive capabilities for dermal exposure assessments, particularly for large or protein-bound substances.