Weekly Calcifediol 100 µg in Women with Vitamin D Deficiency: A Post Hoc Analysis of a Randomised Placebo-Controlled Phase II/III Trial

Background/Objective: Given the high prevalence of vitamin D deficiency, particularly among older women, this post hoc analysis was conducted to evaluate the long-term efficacy and safety of weekly calcifediol 100 µg in women with vitamin D deficiency participating in a randomised, double-blind, phase II/III trial. Methods: A total of 261 women were included (calcifediol, n = 192; placebo, n = 69). The primary objective was to compare the proportions of women achieving serum 25(OH)D concentrations ≥20 ng/mL or ≥30 ng/mL over the 12-month treatment period. Exploratory analyses of body mass index (BMI) and menopausal status were performed. Results: Weekly calcifediol 100 µg demonstrated superior efficacy versus placebo from week 4 in women achieving ≥20 ng/mL (68.2% vs. 5.8%; p < 0.001) or ≥30 ng/mL (21.4% vs. 0%; p < 0.001), and consistently higher proportions were maintained through week 52. Mean 25(OH)D concentrations increased from 12.21 ng/mL at baseline to 39.47 ng/mL at week 16, and remained stable (41–43 ng/mL) thereafter. No significant differences were observed across BMI or menopausal status subgroups. The safety profile of weekly calcifediol 100 µg was similar to placebo, with no evidence of toxicity. Conclusions: Weekly calcifediol 100 µg is a safe and effective option for achieving and maintaining adequate vitamin D levels in vitamin D-deficient women over a period of 12 months, and is associated with consistent effects across BMI and menopausal status.