Effect of two prophylactic bolus vitamin D dosing regimens (1000 IU/day vs. 400 IU/day) on bone mineral content in new-onset and infrequently-relapsing nephrotic syndrome: a randomised clinical trial.

OBJECTIVES: To examine the efficacy of two vitamin D dosages (1000 vs. 400 IU/day) for osteoprotection in children with new-onset and infrequently-relapsing nephrotic syndrome (IFRNS) receiving corticosteroids.

METHODS: This parallel-group, open label, randomised clinical trial enrolled 92 children with new-onset nephrotic syndrome (NS) (n = 28) or IFRNS (n = 64) to receive 1000 IU/day (Group A, n = 46) or 400 IU/day (Group B, n = 46) vitamin D (administered as a single bolus initial supplemental dose) by block randomisation in a 1:1 allocation ratio. In Group A, vitamin D (cholecalciferol in a Calcirol® sachet) was administered in a single stat dose of 84,000 IU on Day 1 of steroid therapy (for new-onset NS), calculated for a period of 12 weeks@1000 IU/day) and 42,000 IU on Day 1 of steroid therapy (for IFRNS, calculated for a period of 6 weeks@1000 IU/day). In Group B, vitamin D (cholecalciferol in a Calcirol® sachet) was administered as a single stat dose of 33,600 IU on Day 1 of steroid therapy (for new-onset NS, calculated for a period of 12 weeks@400 IU/day) and 16,800 IU on Day 1 of steroid therapy (for IFRNS, calculated for a period of 6 weeks@400 IU/day). The proportionate change in bone mineral content (BMC) was analysed in both groups after vitamin D supplementation.

RESULTS: Of the 92 children enrolled, 84 (n = 42 new onset, n = 42 IFRNS) completed the study and were included in the final analysis. Baseline characteristics including initial BMC, bone mineral density, cumulative prednisolone dosage and serum 25-hydroxycholecalciferol levels were comparable in the two groups. There was a greater median proportionate change in BMC in the children who received 1000 IU/day vitamin D (3.25%, IQR -1.2 to 12.4) than in those who received 400 IU/day vitamin D (1.2%, IQR -2.5 to 3.8, p = 0.048). The difference in proportionate change in BMC was only statistically significant in the combined new-onset and IFRNS, but not for IFRNS alone. There was a greater median proportionate change in serum 25-hydroxycholecalciferol, in the children who received 1000 IU/day vitamin D (20.6%, IQR 14.9-36.75) than in those who received 400 IU/day vitamin D (7.7%, IQR 3.5-18.5, p < 0.01). There was a greater median proportionate change in serum calcium in the children who received 1000 IU/day vitamin D (20%, IQR 13.1-29.0) than in those who received 400 IU/day vitamin D (11.3%, IQR 2.8-25.0, p = 0.03). Despite vitamin D therapy, BMC decreased from the baseline in 15 (32.6%) children receiving 1000 IU/day vitamin D and in 17 (36.9%) children receiving 400 IU/day vitamin D. There were no adverse effects attributable to vitamin D.

CONCLUSION: The 1000 IU/day dose is marginally more effective than 400 IU/day and it is likely than an even larger dose is required. Further research is required to assess the efficacy and safety of vitamin D doses higher than 1000 IU/day.