Which statement about zero-order elimination is true?

Which statement about zero-order elimination is true?

• A. It is less common and has a higher chance of drug accumulation.
• B. It is the most common form of elimination.
• C. It leads to a constant fraction elimination per unit time.
• D. It results in a decreasing half-life with dose.

Answer: (A)

Zero-order elimination means the body removes a fixed amount of drug per unit time, regardless of how much is present. That makes the elimination rate constant and not dependent on concentration, so the drug tends to decline linearly over time. When dosing occurs repeatedly, this fixed elimination amount can be exceeded by the input from each dose, leading to accumulation—especially at higher doses or with a short dosing interval. This behavior contrasts with the more common first-order kinetics, where the elimination rate is proportional to the concentration and the drug declines exponentially with a constant half-life. Thus, the statement that zero-order elimination is less common and has a higher chance of drug accumulation is true. The other ideas don’t fit: zero-order is not the most common form of elimination; it does not eliminate a constant fraction per unit time (that’s first-order); and the half-life does not decrease with dose—in zero-order it typically changes with dose (often increasing as dose increases).

Zero-order elimination means the body removes a fixed amount of drug per unit time, regardless of how much is present. That makes the elimination rate constant and not dependent on concentration, so the drug tends to decline linearly over time. When dosing occurs repeatedly, this fixed elimination amount can be exceeded by the input from each dose, leading to accumulation—especially at higher doses or with a short dosing interval. This behavior contrasts with the more common first-order kinetics, where the elimination rate is proportional to the concentration and the drug declines exponentially with a constant half-life.

Thus, the statement that zero-order elimination is less common and has a higher chance of drug accumulation is true. The other ideas don’t fit: zero-order is not the most common form of elimination; it does not eliminate a constant fraction per unit time (that’s first-order); and the half-life does not decrease with dose—in zero-order it typically changes with dose (often increasing as dose increases).