Drug levels during the course of a dosing interval. Drug levels during the course of a dosing interval. The drug concentration is lowest (Cmin) just before the dose is taken, then rises to a peak level (Cmax) at a certain time after the dose (Tmax). The concentration then falls back to Cmin before the next dose. The area under the concentration-time curve (AUC) describes total drug exposure during the entire dosing interval. Jeffrey Schiff et al. CJASN 2007;2:374-384 ©2007 by American Society of Nephrology