Why is AUC the preferred PK metric for time-dependent antibacterial effects?

• A. AUC captures overall exposure and correlates with efficacy for time-dependent drugs
• B. Cmax is more important
• C. Trough is best
• D. Half-life determines outcome

Answer: (A)

For time-dependent antibacterial effects, the total exposure to the drug over a dosing interval drives efficacy more than how high the peak concentration rises. AUC, by integrating concentration over time, captures this overall exposure—combining both how much drug is present and for how long it stays there. Because the antibacterial effect tracks with the amount of exposure the bacteria experience across the entire interval, AUC correlates with how well the drug works across different dosing regimens. This makes AUC a reliable single metric to predict efficacy for time-dependent drugs, since it accounts for variations in clearance, absorption, and distribution that change exposure over time. In contrast, focusing on the peak (Cmax) emphasizes only the highest concentration, which is more relevant for concentration-dependent drugs; trough concentration alone reflects the minimum level but not the total exposure; and half-life tells you how long levels persist but not how much exposure occurs in total. So, AUC best represents the integrated exposure that drives the time-dependent antibacterial response.