Area under the curve represents the total drug concentration in blood plasma over a given time.
AUC is the concentration and time the concentration of an antibiotic remains above the MIC after any one dose (see AUC/MIC and PK/PD). It is dependent on the bioavailability and clearance of the drug from the body: the higher the bioavailability i.e., lower clearance, the higher the AUC and vice versa. The drug concentration is measured at discrete points in time and the data plotted as concentration vs. time. The trapezoidal rule is used to determine the AUC.