The single-compartment model assumes the human body is a single well-stirred open compartment. When a drug administered through IV bolus enters the body, it distributes instantaneously without barriers and leaves the body through biotransformation and elimination. The volume of the compartment is the apparent volume of distribution—a theoretical volume that the administered dose can rapidly and uniformly distribute into. Drug clearance from the body follows first-order kinetics, where the elimination rate is directly proportional to the drug concentration in the body. With time, drug plasma concentration declines exponentially with a proportional decline in the tissue drug concentration. A continuous infusion of a given dose attains a steady-state value exponentially. If infusion stops, the concentration falls exponentially. If the same dose is administered in multiple equal doses, the mean steady-state concentration and the time required to reach the steady state are similar to that of a continuous infusion.