Regarding drugs with first-order elimination, which statement is true about drug clearance?

The statement that defines drug clearance in terms of first-order elimination correctly emphasizes the relationship between the elimination rate of a drug and its concentration in the serum. In first-order kinetics, the rate of elimination is proportional to the serum concentration; as such, clearance can be calculated using the formula: clearance equals the elimination rate divided by the serum level of the drug. This relationship shows that as the serum concentration decreases, the elimination rate also decreases proportionally, which is characteristic of first-order elimination.

The other options do not accurately represent the concept of drug clearance in the context of first-order elimination. For example, the assertion about clearance being performed by the stomach misrepresents where drug elimination primarily occurs, as elimination is mainly a hepatic and renal process. The statement linking clearance directly to bioavailability overlooks the fact that while bioavailability affects the amount of drug reaching systemic circulation, clearance is more focused on the process of elimination from the body. Lastly, the correlation of clearance rate with drug dose does not hold true; in first-order kinetics, the clearance remains constant regardless of the dose, as it is an intrinsic property of the drug and the individual’s metabolic capacity. Therefore, the first option succinctly captures the essential principle of drug clearance in the context of first-order