Which statement best describes zero-order elimination?

• A. The elimination rate is constant and independent of concentration
• B. The elimination rate increases with concentration
• C. The elimination rate decreases with concentration
• D. The elimination rate is proportional to square of concentration

Answer: (A)

Zero-order elimination happens when the body's drug‑processing pathways are saturated, so they can remove only a fixed amount of drug per unit time regardless of how much drug is present. Because the capacity is capped, increasing the concentration doesn’t speed things up; the rate remains constant. That’s why the elimination rate is constant and independent of concentration. In contrast, when the system isn’t saturated, the rate depends on how much drug is there (first-order), or would depend even more steeply in other hypothetical cases (second-order). So describing a constant amount removed per hour, regardless of concentration, is the hallmark of zero-order kinetics.