Continuous Intestinal Absorption Model Based on the Convection-Diffusion Equation

Area of Science:

• Pharmacokinetics and Drug Metabolism
• Computational Biology and Bioinformatics
• Gastroenterology and Hepatology

Background:

• Accurate prediction of oral drug absorption is crucial for drug development.
• Existing models often struggle to capture the complex interplay between drug properties and intestinal physiology.

Purpose of the Study:

• To develop and validate a continuous intestinal absorption model.
• To incorporate enterocyte membrane, intracellular lipids, and transporter dynamics.
• To predict drug fraction absorbed and concentration-time profiles.

Main Methods:

• Developed a continuous model based on the convection-diffusion equation.
• Integrated physiological parameters (velocity, diffusion, pH, surface area) along the intestine.
• Included active uptake (OATP2B1) and efflux (P-gp) transporters.
• Modeled both solution and solid oral drug dosing, including dissolution.

Main Results:

• Predicted fraction absorbed with 81% accuracy (90% without outliers) for oral and colonic dosing.
• Achieved high exposure overlap coefficients (>0.9) for most solution and solid dose formulations.
• Successfully predicted drug precipitation and improved predictions when transporters were included.
• Recapitulated relationships between absorption, permeability, solubility, and particle size.

Conclusions:

• The developed model provides a robust framework for predicting intestinal drug absorption.
• It effectively integrates drug physicochemical properties and intestinal physiological factors.
• This model can enhance the prediction of drug efficacy and safety in preclinical and clinical settings.