Determination of Hepatitis B Immunoglobulin Infusion Interval Using Pharmacokinetic Half-life Simulation for Posttransplant Hepatitis B Prophylaxis

Background: Prophylaxis for hepatitis B virus (HBV) recurrence is essential after liver transplantation (LT) in HBV-associated recipients. This study established an individualized HBV prophylaxis protocol, through optimization of hepatitis B immunoglobulin (HBIG) administration, with application of simulative half-life (SHL). Methods: This study involved five parts: Part 1 developed the SHL estimation method with 20 patients; Parts 2 and 3 assessed the SHL variability and developed a simulation model to apply SHL in 100 patients; Part 4 validated the simulation model in 114 patients, and Part 5 was a cross-sectional study on the current status of HBIG infusion intervals in 660 patients. Results: In Part 1, infusion of 10,000 IU HBIG induced add-on rise hepatitis B surface antibody (anti-HBs) titer of 5,252.5 +/- 873.7 IU/L, which was 4.4% lower than actual measurement. Mean SHL of 20.0 +/- 3.7 days was 2.2% longer than actual measurement. In Part 2, the medians of the intra- and inter-individual coefficient of variation in SHL were 13.5% and 18.5%, respectively. Pretransplant HBV DNA load and posttransplant antiviral therapy did not affect SHL. In Part 3, a simulation model was developed to determine the interval of HBIG infusion, by using SHL. In Part 4, all 114 patients were successfully managed with regular HBIG infusion intervals of >= 8 weeks, and the interval was prolonged to >= 12 weeks in 89.4%, with a target trough anti-HBs titer >= 200 IU/L. In Part 5, 47.4% of our patients received HBIG excessively, at a target trough titer of 500 IU/L. Conclusion: SHL estimation using only clinically available parameters seems to be reliably accurate when compared with actual measurements. We believe that SHL estimation is helpful to establish a personalized HBV prophylaxis protocol for optimizing HBIG administration.