The negative slope of a concentration-time curve is also known as which of the following?

The negative slope of a concentration-time curve is also known as which of the following?

• A. Elimination rate
• B. Absorption rate
• C. Half-life
• D. Clearance

Answer: (C)

In first-order elimination, the drug concentration decays exponentially over time. If you plot the natural log of concentration versus time, you get a straight line with a negative slope. That slope is the elimination rate constant, k, which quantifies how quickly the drug is cleared from the body. The faster the elimination, the larger the magnitude of this slope. The half-life, t1/2, is not the slope itself but is related to it by t1/2 = 0.693/k. So you derive the half-life from the slope, but they are distinct quantities—the slope reflects the elimination rate constant, and the half-life tells you how long it takes for the concentration to drop by half. Therefore, the negative slope best corresponds to the elimination rate constant (with half-life being a derived parameter from that slope).

In first-order elimination, the drug concentration decays exponentially over time. If you plot the natural log of concentration versus time, you get a straight line with a negative slope. That slope is the elimination rate constant, k, which quantifies how quickly the drug is cleared from the body. The faster the elimination, the larger the magnitude of this slope.

The half-life, t1/2, is not the slope itself but is related to it by t1/2 = 0.693/k. So you derive the half-life from the slope, but they are distinct quantities—the slope reflects the elimination rate constant, and the half-life tells you how long it takes for the concentration to drop by half.

Therefore, the negative slope best corresponds to the elimination rate constant (with half-life being a derived parameter from that slope).