Tacrolimus area under the concentration versus time curve monitoring, using home-based volumetric absorptive capillary microsampling.

Therapeutic drug monitoring (TDM) of tacrolimus (Tac) is mandatory in renal transplant recipients (RTxR). Area under the concentration versus time curve (AUC) is the preferred measure for Tac exposure; however, for practical purposes, most centers use trough concentrations as a clinical surrogate. Limited sampling strategies (LSS) in combination with population pharmacokinetic model-derived Bayesian estimators (popPK-BE) may accurately predict individual AUC. The use of self-collected capillary microsamples could simplify this strategy. This study aimed to investigate the potential of AUC-targeted Tac TDM utilizing capillary microsamples in combination with popPK-BE METHODS:: A single center prospective pharmacokinetic study was conducted in standard-risk RTxR (n=27) receiving Tac twice daily. Both venous and capillary microsamples (Mitra, Neoteryx, Torrance, CA) were obtained across two separate 12-h Tac dosing intervals (n=13 samples/AUC). Utilizing popPK-BE, reference AUC (AUCref) was determined for each patient using all venous samples. Different LSS were tested for AUC predictions: 1) the empiric sampling scheme; 0, 1, and 3 h post-dose and 2) three sampling times determined by the multiple model optimal sampling time function in Pmetrics. Agreement between the predicted AUCs and AUCref were evaluated using C-statistics. Accepted agreement was defined as a total deviation index ≤ ±15%.The AUC from capillary microsamples revealed high accuracy and precision compared to venous AUCref, and 85% of the AUCs had an error within ±11.9%. Applying microsamples at 0, 1, and 3 h post-dose predicted venous AUCref with acceptable agreement. Patients performed self-sampling with acceptable accuracy.Capillary microsampling is patient-centered, making AUC-targeted TDM of Tac feasible without extended hospital stays. Samples obtained 0, 1, and 3 h post-dose, combined with popPK-BE accurately predict venous Tac AUC.