POPULATION PHARMACOKINETICS OF 25-HYDROXY VITAMIN D IN NON-ELDERLY POSTMENOPAUSAL WOMEN

Introduction/aim: The aims of this study were to develop a population pharmacokinetic (PPK) model for the clearance of 25-hydroxy vitamin D in non-elderly postmenopausal women and to identify the factors which have a significant influence on its clearance. Methods: The study population consisted of postmenopausal women who had been referred for evaluation of bone mineral density (BMD) by DEXA (dual-energy x-ray absorptiometry) scanner. The population pharmacokinetics modelling was conducted using the ADVAN 1 subroutine from a non-linear mixed effects (NONMEM) program, and thirty-two covariates were assessed. Results: A total of 75 serum concentrations were obtained from the same number of postmenopausal women and used for PPK analysis. The mean values of the participants’ age was 57.92±3.93 years and their body weight was 69.76±11.49kg. A wide range of 25-hydroxy vitamin D concentrations was observed (from 3.41 to 61.92ng/mL) with a mean value of 26.19±10.95ng/mL. A total of 32 covariates were examined and preliminary results suggested the influence of six covariates on 25-hydroxy vitamin D clearance. In the final PPK model however, only one covariate was shown to have a significant impact on the clearance value – the mean daily dietary intake dose of vitamin D (DD). Conclusions: These findings offer a preliminary basis on which to determine the level of vitamin D supplementation required by individual postmenopausal women. It could prove particularly important in achieving optimal serum levels of vitamin D in this vulnerable population.