Evaluation of 14-day Concentration-time Curves of Vitamin D<inf>3</inf> and 25-Hydroxyvitamin D<inf>3</inf> in Healthy Adults With Varying Body Mass Index

Abstract

Background/Aim: To analyze the concentration-time curves of single-dose oral 25(OH)D3 in comparison with vitamin D3 in healthy adults. Patients and Methods: The pharmacokinetics observed over two weeks after orally administering single 900 μg doses of vitamin D3 and 25(OH)D3 to six otherwise healthy vitamin D insufficient/deficient adults participating in a broader randomized, double-blind, crossover, single center trial was analyzed. The study protocol was approved by the institutional review board (H-37167). Results: Individual concentration-time curves revealed that vitamin D3 took longer than 25(OH)D3 to reach its maximal concentration after ingestion in five participants. After 25(OH)D3 ingestion, 25(OH)D3 reached its maximal concentration, dropped rapidly, and plateaued before starting to decrease slowly. There were observable inter-individual variations in the bioavailability of vitamin D3 and 25(OH)D3 and the pattern of changes in 25(OH)D3 concentration after their ingestion. Conclusion: Pharmacokinetics of 25(OH)D3 in comparison with vitamin D3 was illustrated and described in this study.