Which pharmacodynamic parameter combines drug exposure with MIC to describe activity?

• A. AUC/MIC
• B. Cmax/MIC
• C. Time above MIC
• D. MIC

Answer: (A)

AUC/MIC is the pharmacodynamic measure that integrates how much drug exposure occurs over time with how sensitive the target bacteria are. The AUC (area under the concentration–time curve) represents total drug exposure within a dosing interval, and the MIC is the minimum concentration that inhibits growth. Taking their ratio ties together the amount of drug the organism experiences and its susceptibility, making AUC/MIC a strong predictor of antibacterial efficacy across regimens and organisms. This integrated exposure–response view is why AUC/MIC is especially useful for drugs where overall exposure drives effect, such as fluoroquinolones and vancomycin.

Time above MIC emphasizes how long concentrations stay above the MIC and is more relevant for time-dependent drugs; Cmax/MIC highlights the peak concentration relative to MIC, important for concentration-dependent drugs; MIC alone only reflects potency without regard to how much exposure is delivered.