Estimating of sample size
In accordance with FDA requirements for bioequivalence study, the geometric mean ratio (GMR) is usually set at 95-105% under these conditions (80% power, α=5%). The intra-subject variability (intra-CV) for gefitinib is described to be 17-30%[7], and the sample size calculation was carried out based on the smallest even number of subjects. Additionally, considering the subject withdrawal of 10%, thus forty healthy male subjects were enrolled in the fasting or fed group. Random order list was calculated by SAS statistical software (version 9.4, SAS Institute, Cary, North Carolina), and all participants were allocated into either a T or R group.