FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam 2025 - Free NABP Practice Questions and Study Guide

A one-compartment model in pharmacokinetics is characterized by the assumption that the body acts as a single, homogenous unit where the drug distributes uniformly throughout the system. This model implies that the drug rapidly equilibrates between the bloodstream and the tissues, reflecting an instantaneous distribution.

When a drug is administered, it enters the central compartment (usually represented by blood and the directly perfused organs). In a one-compartment model, the concentration of the drug in this central compartment changes rapidly after administration and reaches a steady state relatively quickly. This rapid equilibration allows for the simplification of calculations and predictions regarding the drug’s concentration over time.

The understanding of a one-compartment model is crucial in contexts where the kinetics of drug distribution can significantly influence therapeutic effectiveness and safety. It simplifies the analysis because there aren’t multiple phases (as seen in more complex models), and you can generally use a single equation to describe the drug's pharmacokinetics, making it easier to predict how a drug will behave in the body.

Other choices describe characteristics that do not align with the definition of a one-compartment model. The biphasic serum level decay curve indicates a two-compartment or multi-compartment model where the drug behaves differently in distinct compartments over time