From the National Osteoporosis Society guidelines and the BNF:
Ergocalciferol = Vitamin D2 – plant-derived. Hard to get hold of as a single preparation, but comes in strengths of 10 000 IU (250 mcg) or 50 000 IU (1.25 mg)
Colecalciferol = Vitamin D3 – animal-derived – the recommended form of supplementation (levels easier to measure, better tissue bioavailability, slower clearance). Desunin and Fultium-D3 both come as tablets of 20 mcg (800 IU)
Alfacalcidol – activated form – not recommended for supplementation. (The specific reason for this wasn’t given – it was lumped in with annual Vitamin D injections as being strategies that weren’t recommended because of either ineffectiveness or high risk of toxicity, but it doesn’t say which is the reason in this case.) Used only in patients with severe renal impairment who can’t activate the other supplements themselves.
Calcitriol = 1, 25-dihydroxyVitamin D – as above
Calciferol – covers either D2 or D3
10 mcg = 400 IU
Loading dose (used only in patients who are symptomatic or who are about to start treatment with a powerful bone resorptive agent): 280 000 – 300 000 IU over several wks. Recommended opti0ns include:
- 1 x 50 000 IU capsule once weekly for 6 weeks
- 2 x 20 000 IU capsules once weekly for 7 wks
- 5 x 800 IU caps daily for 10 wks
Maintenance dose: start 1 month after loading: 800 – 2000 IU daily. Can be given either daily or as intermittent higher doses.
Monitoring: Serum calcium 1 month after completion of loading dose, or 1 month after treatment commences if no loading dose given. (This is to pick up primary hyperparathyroidism unmasked by the supplementation.) Vitamin D after 3 – 6 months treatment.
Calcium: Obviously, don’t try to do the loading dose with combination preparations or patient will be completely overloaded with calcium. As for maintenance regimes, apparently the jury remains out on whether additional calcium increases MI risk, and it does increase the risk both of renal stones and of non-compliance, but there is some evidence it may decrease overall mortality.
Cautions: Granulomatous disease (TB, sarcoidosis) increases the risk of hypercalcaemia due to increased 1-alpha-hydroxylase activity (which converts the Vitamin D to its activated form) – seek specialist advice before starting supplementation.