Abstract: OBJECTIVE To evaluate missed and remedial dosage regimens of apatinib by Monte Carlo simulation(MCS) method, to provide theoretical basis for clinical rational use of drugs. METHODS According to population pharmacokinetic(PPK) model of apatinib(850 mg, qd, po), 5 000 MCS were estimated for various scenesfull compliance, missed doses without remediation, remedial dosage regimens(6, 12, 18 h), and 24 h double doses the next day by NONMEM for patients with advanced metastatic gastric cancer after gastric surgery. The proportion of people outside the individual treatment window(ITW) and duration outside the ITW(the duration was based on >5% of the population, the same below) of the missed and remedial regimens were calculated, and the rationality of each scenario were analyzed. RESULTS Predicted concentration continues to be stable within ITW in full compliance. When missed one dose without remediation, the fluctuation of predicted concentration was increased, and the proportions of people below ITW were 46.26%(the same day) and 7.52%(the next day), and the duration were 24.4 h(the same day) and 1.6 h(the next day). After taking the medicine at next time, the concentration can rise and be stable within ITW. When one dose was missed, the proportion of people under ITW and the duration were increased with the prolongation of remedial time before remediation,and the proportion of people above ITW and the duration were increased with the prolongation of remedial time after remediation. CONCLUSION According to the results of apatinib MCS, patients should improve medication adherence and avoid missed medications for avoiding the increased fluctuation of blood concentration because of missed dose and remadiation. If the time of missed dose was too long, remedial dosage regimens or double dose supplementation is not recommended, just take the medicine normally the next day.