Which elimination model do drugs rapidly infused intravenously usually follow?

Drugs that are rapidly infused intravenously typically follow a biphasic or two-compartment elimination model. This model is characterized by two distinct phases of drug elimination from the body. The first phase involves a rapid decline in serum drug concentration, primarily due to distribution into well-perfused tissues and organs. It reflects how quickly the drug is leaving the central circulation and entering other body compartments. After this initial phase, the second phase occurs, where the drug concentration decreases more slowly as it distributes into deeper tissues and is gradually eliminated through metabolism and excretion.

Understanding this elimination model is essential as it highlights the different dynamics of drug distribution and clearance. The rapid fall in serum levels during the first phase is significant in clinical settings, as it helps predict how quickly a drug will attain its therapeutic effect and how long it will remain in the system.

The other models mentioned do not typically apply to the behavior of drugs given via rapid intravenous infusion. For instance, the one-compartment models assume uniform distribution and elimination rates, which do not account for the complex dynamics observed with many drugs. The Michaelis-Menton model indicates nonlinear kinetics, which is not characteristic of most drugs during initial rapid infusion phases, as they tend to follow first-order elimination until saturation occurs.