Novel Population Pharmacokinetic Method Compared to the Standard Noncompartmental Approach to Assess Bioequivalence of Iron Gluconate Formulations

ABSTRACT- Purpose: Iron-containing products are atypical in terms of their pharmacokinetic properties because iron is only removed by plasma sampling and is non-linear. This study aims to present a novel way of assessing the relative bioavailability of two sodium ferric gluconate complex (SFGC) formulations and compare this approach to a standard previously published noncompartmental approach. Methods: Data were from open-label, randomized, single-dose studies (Study 1 was parallel whereas Study 2 was crossover). Subjects with low but normal iron levels were infused IV SFGC in sucrose by GeneraMedix Inc. and/or Ferrlecit ® Injection (Watson Laboratories Inc.). In Study 1 (n=240), 125 mg was infused over 10 minutes. In Study 2 (n=29), 62.5 mg was infused over 30 minutes. Samples were assayed for total iron (TI) and transferrin-bound iron (TBI) over 36 hours (Study 1) or 72 hours (Study 2) post-dose. Studies 1 and 2 used standard noncompartmental analysis. Study 2 also used population PK (PPK) analyses with ADAPT 5®. The final model predicted SFGC area-under-the-curve (AUCpred) and maximal concentration (Cmaxpred). Analyses of variance was conducted on ln-transformed PK parameters. Ratios of means and 90 % confidence intervals (CIs) were estimated. Bioequivalence was demonstrated if values were within 80-125%. Results: For Study 1, ratios and 90 % CIs for TI baseline-corrected Cmax and AUC0-36 were 100.4 (96.5 – 104.5) and 99.7 (94.2 – 105.5). For TBI, results for TI baseline-corrected Cmax and AUC0-36 were 86.8 (82.7 – 91.1) and 92.4 (85.6 – 99.7). For Study 2, a multi-compartmental model simultaneously described the PK of TI, TBI and SFGC. Ratios and 90 % CIs for SFG