AIM: To evaluate the missed and remedial dosage regimens in cancer patients using erlotinib population pharmacokinetics (PPK) model by Monte Carlo simulation (MCS). METHODS: According to erlotinib PPK model (150 mg po qd), 10 000 MCS were estimated for missed doses and remedial dosage regimens (6 h, 12 h, 18 h, and 24 h double doses) by NONMEM. The proportion of people outside the individual treatment window (ITW) and duration outside the ITW (>5%) under the missed and remedial regimens were calculated, and the rationality of the supplemental regimen in each scenario were analyzed. RESULTS:When missed taking erlotinib, the drug concentration continued to drop to the next medication time and affected the next day's concentration. The durations below the ITW were 25.1 h and 6.6 h, respectively. The proportion of people below ITW increased from 6.82% to 14.55%, and the duration time increased from 5.9 h to 23.6 h; the proportion of people above ITW increased from 5.99% to 10.74%, and the duration time increased from 3.7 h to 9.7 h. CONCLUSION: According to MCS results, patients should improve erlotinib medication compliance and avoid missed doses. In case of missed dose, remedial should be given as soon as possible, but it is not recommended to take remedial or double dosage near the next administration time to avoid increased adverse drug reactions.

Objective To establish a quality control method for monitoring the blood concentrations of cyclosporin A and tacrolimus by HPLC-MS/MS,and to evaluate the quality control samples using the Westgard multi-rule theory.Methods HPLC-MS/MS was used to determine the concentration of cyclosporin A and tacrolimus in human whole blood.The quality control samples of low,medium and high concentration levels in the therapeutic drug monitoring process were statistically analyzed,Levery-Jennings and Z-score quality control charts were drawn,and the Westgard multi-rule theory was applied for in-house quality control evaluation.Results The established method was fully validated with linear ranges of 10.40-1 040.00 ng·mL-1 and 0.50-49.50 ng·mL-1,the quantification limits were 10.40 and 0.50 ng·mL-1,respectively.The extraction recoveries were 108.61％-113.24％and 101.99％-109.37％,respectively.The matrix factors normalized by internal standard were 106.68％-111.27％and 95.70％-97.81％for cyclosporin A and tacrolimus,respectively.The intra-day and inter-day accuracy and precision were less than 15.0％.Other parameters were also validated and met the acceptance criteria.Levery-Jennings and Z-score quality control charts showed that there were 4 warnings(violation of the 12s rule)in the results of the 26 groups of quality control samples in the third quarter of 2022,and no phenomenon was observed to be out of control.Conclusion The established in-house quality control system for therapeutic drug monitoring of cyclosporin A and tacrolimus can effectively ensure the accuracy of blood drug concentration detection.