How well are the optimal serum 25OHD concentrations reached in high-dose intermittent vitamin D therapy? a placebo-controlled study on comparison between 100 000 IU and 200 000 IU of oral D3 every 3 months in elderly women
Clinical Endocrinology DOI: 10.1111/cen.13014
Matti J. Välimäki
Objective: Intermittent dosing may improve adherence to vitamin D therapy. Dosing regimen should maintain optimal serum 25-hydroxyvitamin D (25OHD) levels over all the year. We compared two dosing regimens, the primary outcome being the percentage of 25OHD measurements reaching the targets of 75 nmol/L or 50 nmol/L after baseline.
Design: Randomized, placebo-controlled parallel group comparison.
Patients: Sixty women aged 75.0 ± 2.9 years.
Interventions: 100 000 IU (group 1D) or 200 000 IU (2D) of vitamin D3 or placebo orally every three months plus calcium 1 gram daily for one year.
Measurements: Serum 25OHD, 1,25-dihydroxyvitamin D, PTH, sclerostin, ionized calcium, urinary calcium, renal function, bone turnover markers.
Results: Serum 25OHD increased, but the difference between two doses was of borderline significance (P=0.0554; area under curve analysis). Immediate post-administrative increases were higher in the 2D vs. 1D group (P<0.05) after 3 and 6 months’ dosing. In the 1D and 2D groups 51.2% and 57.7% of all on-treatment measurements reached the target of 75 nmol/L. PTH levels differed marginally (P=0.0759) due to tendency to lowering immediately after vitamin D boluses. Urinary calcium differed between the groups (P=0.0193) due to increases one week after vitamin D dosing.
Conclusions: The doses of 100 000 or 200 000 IU of oral cholecalciferol every 3 months were not capable of stabilizing 25OHD levels over the target of 75 nmol/L over the year. To improve the efficacy of high-dose vitamin D therapy the interval between boluses has to be shortened instead of increasing their size.
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