Steady state is achieved when the amount of drug absorbed equals the amount cleared from the body. Which option best reflects this?

Steady state is achieved when the amount of drug absorbed equals the amount cleared from the body. Which option best reflects this?

• A. When the distribution equals clearance
• B. When the amount absorbed equals the amount cleared
• C. When the drug concentration reaches a peak
• D. When absorption stops

Answer: (B)

Steady state means the rate at which the drug enters the body matches the rate at which it is removed, so the amount in the body stays constant over time. The statement that the amount absorbed equals the amount cleared captures that balance directly—the input rate equals the elimination rate, leading to a constant plasma level after enough dosing. This differs from a peak concentration, which is a transient high level after a dose before steady state is reached. If absorption stops, input drops and the drug is cleared, so levels fall rather than stay constant. Distribution isn’t about balancing input and elimination, so it doesn’t describe steady state.

Steady state means the rate at which the drug enters the body matches the rate at which it is removed, so the amount in the body stays constant over time. The statement that the amount absorbed equals the amount cleared captures that balance directly—the input rate equals the elimination rate, leading to a constant plasma level after enough dosing.

This differs from a peak concentration, which is a transient high level after a dose before steady state is reached. If absorption stops, input drops and the drug is cleared, so levels fall rather than stay constant. Distribution isn’t about balancing input and elimination, so it doesn’t describe steady state.