Area under the curve

In the field of pharmacokinetics, the area under the curve (AUC) is the area under the curve in a plot of concentration of drug in plasma against time.

Mathematical definition

Mathematically, this value is a measure of the integral of the instantaneous concentrations during a time interval and has the unit (mass/volume)*time . AUC is usually given for the time interval zero to infinity, and other time intervals are indicated (for example AUC (t_{1,t2) where t1 and t2 are the starting and finishing times for the interval). Clearly plasma drug concentrations cannot be measured 'to infinity' for a patient or experimental subject so mathematical approaches are used to estimate the AUC from a limited number of concentration measurements.}

Interpretation and usefulness of AUC values

In real-world terms the AUC (from zero to infinity) represents the total amount of drug absorbed by the body, irrespective of the rate of absorption. This is useful when trying to determine whether two formulations of the same dose (for example a capsule and a tablet) release the same dose of drug to the body. Another use is in the therapeutic monitoring of toxic drugs. For example, gentamicin is an antibiotic which displays nephro- and ototoxicities; measurement of gentamicin concentrations in a patient's plasma and calculation of the AUC is used to guide the dosage of this drug.

AUC becomes useful for knowing the average concentration over a time interval, AUC/t. Also, AUC is referenced when talking about elimination. The amount eliminated by the body = clearance (volume/time) * AUC (mass*time/volume).