Sensitivity of Estimated Tacrolimus Population Pharmacokinetic Profile to Inaccurate Assumptions about Dose Timing and Absorption: An Investigation in Real-World and Simulated Data

A population pharmacokinetic (PK) study with 363 subjects was performed using real-world data extracted from electronic heath records (EHRs) to estimate the tacrolimus population PK profile. As population PK studies for oral medications performed using EHR data often assume a regular dosing schedule as prescribed without incorporating exact dosing time, we assessed the sensitivity of the PK parameter estimates to assumptions about dose timing using last-dose times extracted by our own natural language processing system, medExtractR . We also investigated the sensitivity of estimations to absorption rate constants that are often fixed at a published value in tacrolimus population PK analysis. There was no appreciable difference in parameters estimates with vs . without last-dose time incorporated in the data and our sensitivity analysis revealed little difference between parameters estimated assuming a range of absorption rate constants. We also conducted simulation studies to investigate how drug PK profiles and experimental designs such as concentration measurements affects sensitivity to incorrect assumptions about dose timing and absorption rates. Our findings suggest that drugs with a slower elimination rate (or a longer half-life) are less sensitive to dose timing errors and that experimental designs which only allow for trough blood concentrations are usually insensitive to deviation in absorption rate.