Correction of vitamin D insufficiency with combined strontium ranelate and vitamin D3 in osteoporotic patients.

Objective: This study aims to investigate the efficacy and safety of oral fixed-dose combination of strontium ranelate 2  g/vitamin D₃ 1000  IU daily vs strontium ranelate 2  g daily for correcting vitamin D insufficiency in osteoporosis.

Design: A 6-month international, randomized, double-blind, parallel-group, phase 3 study.

Methods: A total of 518 men and postmenopausal women aged ≥50 years with primary osteoporosis (T-score ≤-2.5 s.d.) and serum 25-hydroxyvitamin D (25(OH)D) >22.5 nmol/l were included. Patients were allocated to strontium ranelate 2 g/vitamin D₃ 1000  IU daily (n=413) or strontium ranelate 2 g daily (n=105). The participants received calcium 1 g daily. The primary endpoint was serum 25(OH)D at last post-baseline evaluation during 3 months.

Results: Both groups were comparable at baseline. Mean baseline of 25(OH)D was 44.1 ± 14.6 nmol/l. After 3 months, the percentage of patients with 25(OH)D ≥50 nmol/l was higher with strontium ranelate/vitamin D₃ vs strontium ranelate (84 vs 44%, P<0.001; adjusted between-group odds ratio=6.7; 95% CI, 4.2-10.9). The efficacy of the fixed-dose combination on 25(OH)D was maintained at 6 months (86 vs 40%, P<0.001). Mean 25(OH)D was 65.1 and 49.5 nmol/l, respectively, after 3 months and 66.9 and 45.4 nmol/l after 6 months. Physical performance improved in both groups. Falls were 17 and 20% in the strontium ranelate/vitamin D₃ and strontium ranelate groups respectively. Parathyroid hormone levels were inversely correlated with 25(OH)D. No clinically relevant differences in safety were observed.

Conclusions: This study confirms the efficacy and safety of fixed-dose combination of strontium ranelate 2 g/vitamin D₃ 1000 IU for correction of vitamin D insufficiency in osteoporotic patients.