2.4. Pharmacokinetic analyses

In the two cohorts, PK assessment consisted of a single‐dose‐administration on Cycle 1, Day 1's (C1, D1) test and a continuous‐dose‐administration on Cycle 1, Day 15′s (C1, D15) test. For detailed blood collection administration, see the supplementary materials. Upon collection, the samples were centrifuged and plasma frozen at a refrigeration of −80 ± 5°C until further analysis. Apatinib and gefitinib plasma concentrations were measured using a confirmed liquid chromatography–tandem mass spectrometry method. PK parameters, including maximum plasma concentration (C _max), area under the plasma concentration‐time curve (AUC), time to reach maximum plasma concentration (T _max), elimination half‐life (T _1/2), steady state concentration (Css), area under the plasma concentration‐time curve for steady state (AUCss), steady state volume of distribution (Vdss), and steady state clearance rate (CLss) were calculated using non‐compartmental methods with Winnonlin 7 software. The AUC was estimated by using the linear trapezoidal rule method and T _1/2 was determined by linear regression of the terminal slope of the logarithmic plasma concentration‐time profile. Descriptive statistics were measured for the PK parameters using mean with its corresponding standard deviation (SD).