Compartmental Models in Pharmacokinetics

Compartmental models in pharmacokinetics simplify drug distribution and elimination using one-compartment and multi-compartment approaches.

Introduction

• Compartmental models are pharmacokinetic models that represent the body as interconnected compartments, each grouping tissues or organs with similar drug distribution and elimination properties.
• Drug movement is modeled using first-order rate constants, helping predict drug concentrations, optimize dosing, and support drug development.

Types of Compartmental Models

1. Mammillary Model

   • Features a central compartment with peripheral compartments connected to it (resembling a star pattern).
   • Suitable for drugs with rapid distribution and elimination, often used for intravenous administration.
   • Compartments represent tissues/organs assumed to have uniform drug behavior.
   • Flexible—more compartments can be added as needed.
     

2. Catenary Model

   • Consists of compartments arranged in a linear sequence (like a chain).
   • Suitable for drugs with slower distribution and elimination, commonly used for oral drugs.
   • Compartments also represent homogeneous tissues/organs.
   • Can be expanded by adding more compartments.
     

Advantages of Compartmental Models

1. Simplification – Provides an easier representation of complex pharmacokinetics.
2. Predictive Power – Estimates drug concentration over time, aiding dose adjustments.
3. Flexibility – Adaptable for IV, oral, and other administration routes.

Disadvantages of Compartmental Models

1. Limited Physiological Relevance – Abstract representation may not fully reflect real physiological processes.
2. Assumptions – Based on first-order kinetics, which may not apply to all drugs.
3. Data Requirements – Needs extensive data for accurate pharmacokinetic parameter estimation.

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