A new physiologically based, segregated-flow model to explain route-dependent intestinal metabolism

Area of Science:

• Pharmacokinetics
• Drug Metabolism and Transport
• Physiologically Based Modeling

Background:

• Existing models struggle to predict route-dependent intestinal metabolism, where oral drug metabolism differs significantly from systemic dosing.
• Understanding intestinal absorption, metabolism, and secretion is crucial for oral drug bioavailability.

Purpose of the Study:

• To develop and evaluate a physiologically based, Segregated-Flow Model (SFM) for predicting intestinal drug clearance and bioavailability.
• To examine the influence of intestinal transport, metabolism, and blood flow characteristics on drug disposition.

Main Methods:

• Developed a SFM segregating intestinal blood flow to absorptive (enterocytes) and nonabsorptive regions.
• Compared SFM predictions with a traditional, homogeneous physiologically based model.
• Analyzed the impact of absorption, exsorption, metabolism, and P-glycoprotein secretion on drug availability.

Main Results:

• The SFM accurately explains higher intestinal metabolism for oral versus intravenous dosing.
• Intestinal availability is inversely related to intrinsic clearances for metabolism and exsorption.
• P-glycoprotein secretion effects diminish with rapid drug absorption.

Conclusions:

• The SFM provides a more physiologically realistic representation of the intestine.
• This model elucidates the mechanisms behind route-dependent intestinal drug metabolism.
• SFM enhances predictions of oral drug bioavailability and disposition.