1. One-Compartment Model. Although the one-compartment model is an oversimplification for most drugs, it does serve to illustrate the basic relationships among clearance, volume of distribution, and the elimination half-life (Fig. 7-1: The plasma concentration versus time profile plotted on both linear (red line, left y-axis) and logarithmic (blue line, right y-axis) scales for a hypothetical drug exhibiting one-compartment, first-order pharmacokinetics).
2. Two-Compartment Model. There are two discrete phases in the decline of the plasma concentration (Fig. 7-2: The logarithmic plasma concentration versus time profile for a hypothetical drug exhibiting two-compartment, first-order pharmacokinetics). To account for this biphasic behavior, one must consider the body to be made up of two compartments, a central compartment, which includes the plasma, and a peripheral compartment.
3. Three-Compartment Model. After IV injection of some drugs, the initial, rapid distribution phase is followed by a second, slower distribution phase before the elimination phase becomes evident.
4. In general, the model with the smallest number of compartments or exponents that accurately reflects the data is used.

Basic Principles of Clinical Pharmacology

1. Pharmacokinetic Principles: Drug Absorption and Routes of Administration
2. Drug Distribution
3. Drug Elimination
4. Pharmacokinetic Models
5. Compartmental Pharmacokinetic Models
6. Pharmacodynamic Principles
7. Drug–Receptor Interactions
8. Drug Interactions
9. Clinical Applications of Pharmacokinetic and Pharmacodynamics to the Administration of IV Anesthetics