Pharmacokinetics of oral vitamin D3 and calcifediol

Abstract

AimLong-term pharmacokinetics after supplementation with vitamin D3 or calcifediol (the 25-hydroxyvitamin D3 metabolite) is not well studied. Additionally, it is unclear whether bolus doses of vitamin D3 or calcifediol lead to 25(OH)D3 plasma concentrations considered desirable for fracture prevention (30ng/mL). We therefore investigated plasma pharmacokinetics of 25(OH)D3 during different vitamin D3 and calcifediol supplementation regimens. MethodsIn this seven-arm, randomized, double-blind, controlled parallel-group study, 35 healthy females aged 50–70years (5 per group) received 20μg calcifediol or vitaminD3 daily, 140μg calcifediol or vitaminD3 weekly, for 15weeks, or a single bolus of either 140μg calcifediol, or vitaminD3, or both. 25(OH)D3 plasma concentrations were quantified using LC–MS/MS in 14 clinical visits among all participants. ResultsFor daily (weekly) dosing, the area under the concentration–time curve (AUC0–24h), which is the measure for exposure, was 28% (67%) higher after the first dose of calcifediol than after the first dose of vitamin D3. After 15weeks, this difference was 123% (178%). All women in the daily and weekly calcifediol groups achieved 25(OH)D3 concentrations >30ng/mL (mean, 16.8days), but only 70% in the vitamin D3 daily or weekly groups reached this concentration (mean, 68.4days). A single dose of 140μg calcifediol led to 117% higher 25(OH)D3 AUC0–96h values than 140μg vitamin D3, while the simultaneous intake of both did not further increase exposure. ConclusionsCalcifediol given daily, weekly, or as a single bolus is about 2–3 times more potent in increasing plasma 25(OH)D3 concentrations than vitamin D3. Plasma 25(OH)D3 concentrations of 30ng/mL were reached more rapidly and reliably with calcifediol.