Why Rate of Absorption Inferences in Single Dose Bioequivalence Studies are Often Inappropriate

Purpose. Peak drug concentration (Cmax) measures the extremity of drug exposure and is a secondary indicator of the extent of absorption after area under the concentration time curve (AUC). Cmax serves as the indicator of absorption rate in bioequivalence (BE) studies in the US (1). The use of Cmax, not the time to Cmax(Tmax), as the metric to assess absorption rate causes erratic inferences in BE studies, and incorrect conclusions for some. We can improve BE efficiency (i.e., get the answer right the first time), by properly analyzing the time to Cmax(Tmax) instead of Cmax.