Basic concepts of pharmacokinetic/pharmacodynamic (PK/PD) modelling

Area of Science:

• Pharmacology
• Pharmacometrics

Background:

• Pharmacokinetics (PK) describes drug concentration over time, while pharmacodynamics (PD) relates concentration to effect.
• Understanding PK/PD relationships is fundamental to modern pharmacotherapy and drug development.

Purpose of the Study:

• To establish and evaluate dose-concentration-response relationships using PK/PD modeling.
• To describe and predict drug effect-time courses based on administered doses.

Main Methods:

• Utilizing simple pharmacodynamic models (e.g., Emax, sigmoid Emax) for steady-state conditions.
• Employing complex integrated PK/PD models for non-steady-state conditions, accounting for temporal dissociation.
• Characterizing PK/PD models by link type (direct/indirect), response mechanism (direct/indirect), link information (hard/soft), and parameter time dependency (variant/invariant).

Main Results:

• PK/PD modeling provides a framework to link drug concentration with observed effects.
• Different models are suitable for steady-state versus non-steady-state conditions.
• Four key attributes characterize PK/PD models, aiding in their selection and interpretation.

Conclusions:

• Integrated PK/PD modeling is essential for accurately predicting drug effects, especially when plasma concentrations and effects are temporally dissociated.
• Preference should be given to PK/PD models grounded in physiological processes.
• Expanded use of PK/PD modeling is expected to significantly benefit drug development and applied pharmacotherapy, improving therapeutic outcomes.