The Tolerability and Biochemical Effects of High-dose Bolus Vitamin D2 and D3 Supplementation in Patients with Vitamin D Insufficiency

Objectives: To investigate the practicality and tolerability of high-dose intramuscular (i.m.) vitamin D2 or oral vitamin D3 replacement in vitamin D-insufficient patients, and to evaluate the biochemical efficacy of each formulation.

Methods: Sixty-nine patients with vitamin D insufficiency [25-hydroxyvitamin D (25(OH)D) <40 nmol/L] were recruited from the Rheumatology Outpatient Department of St George's Hospital, London. In study 1, 50 patients received 300 000 IU i.m. vitamin D2 (ergocalciferol). In study 2, 19 patients received 300 000 IU oral vitamin D3 (cholecalciferol) under observation. Biochemical response was measured at baseline, and at 12 and 24 weeks.

Results: Bolus i.m. vitamin D2 or oral vitamin D3 was well tolerated. The change from baseline in serum 25(OH)D was significantly greater at 6 and 12 weeks in study 2 (p<0.0001 and <0.0001, respectively). In study 1, a modest increase in mean serum 25(OH)D at 6, 12, and 24 weeks was observed but no patients achieved a serum 25(OH)D concentration > or = 50 nmol/L. PTH remained elevated in 42% of patients with secondary hyperparathyroidism at 12 weeks. In study 2, 100% and 89% of patients had serum 25(OH)D>50 nmol/L at 6 and 12 weeks, respectively. All patients with elevated baseline PTH were fully suppressed at 12 weeks. No cases of hypercalcaemia were observed in either group.

Conclusion: The 300 000-IU bolus of vitamin D2 or D3 was practical, well tolerated, and safe. Vitamin D3 had greater potency than equimolar vitamin D2, with a higher, sustained serum 25(OH)D response and efficacious PTH suppression. To adequately treat vitamin D insufficiency we would recommend administering 300,000 IU oral vitamin D3 approximately three times per year.