area under the curve
Area under the curve is the total shaded area beneath a plot of plasma concentration against time. If Cmax tells you how high the drug level climbs and Tmax tells you when, AUC rolls the whole curve into a single number that captures total exposure — how much drug, for how long, the body actually experienced.
Mathematically it is the integral of concentration over time, and it has a clean physical meaning: AUC equals the dose that reached the circulation divided by clearance. This makes AUC the natural way to measure bioavailability (compare oral AUC to intravenous AUC) and the key exposure metric in many drug-safety and efficacy thresholds.
Two formulations can share the same AUC yet behave very differently — a fast tablet and a slow-release one may deliver identical total exposure with very different peaks. That is why bioequivalence testing looks at AUC together with Cmax: AUC for the extent of absorption, Cmax (and Tmax) for the rate.
Carboplatin chemotherapy is dosed to a target AUC (using the Calvert formula) rather than by body weight, because total platinum exposure predicts both effect and toxicity better than the milligram amount.
Carboplatin is dosed by target AUC, not weight.
Bioavailability F = (AUC by the test route) / (AUC intravenous), for equal doses. AUC measures extent of exposure; Cmax and Tmax measure rate.