Ergocalciferol dosing

CF patients with low bone mineral density and low serum vitamin D levels may improve bone health through supplemental vitamin D analogs beyond those found in standard CF vitamins. The optimal dose and analog have not been determined. For ergocalciferol, a minimum of 400 IU and 800 IU... 

Vitamin D is often combined in varying amounts with calcium salts. A multiple vitamin is another good source of vitamin D. Most multivitamins contain 400 IU per tablet. Vitamin D is also available as a single entity. Doses above 2000 IU/day should be avoided owing to the risk of hypercalciuria and hypercalcemia. Ergocalciferol (vitamin D2) and... 

VII.a.2.1. Prevention. Vitamin D deficiency can be prevented by dietary supplementation with low doses of vitamin D, usually given as calcium and er-gocalciferol tablets, containing only 10 pg (400 units) of ergocalciferol. 

Early studies showed that, after the administration of [ H]cholecalciferol or ergocalciferol to vitamin D-deficient animals, there is marked accumulation of [ H] calcitriol in the nuclei of intestinal mucosal cells. Physiological doses of vitamin D cause an increase in the intestinal absorption of calcium in deficient animals the response is faster after the administration of calcidiol and faster stUl after calcitriol. There are two separate responses of intestinal mucosal cells to calcitriol a rapid increase in calcium uptake that is due to recruitment of calcium transporters to the cell surface (Section 3.3.2) and a later response from the induction of a calcium binding protein, calbindin-D. 

Horst RL, Napoli JL, and Littledike ET (1982) Discrimination in the metabolism of orally dosed ergocalciferol and cholecalciferol by the pig, rat and chick. Biochemical Journal 204,185-9. 

The hypocalcaemia of hypoparathyroidism may require ergocalciferol in doses up to 2.5 mg (100 000 units) daily to achieve normocalcaemia but the dose is difficult to titrate and hypercalcaemia from overdose may take weeks to resolve. The synthetic vitamin D derivatives, alfacalcidol and... 

Rickets and osteomalacia can be treated with daily oral doses of ergocalciferol (0.01-15.0 mg/day). Treatment is continued for 1 to 3 months and is coupled with adequate levels of dietary calcium and phosphate. Where the disease is due to a defect in 1-hydroxylase, treatment is with l,25-(OH)2D3. 

Vitamins are not synthesized in the body, at least not in the amounts needed. On the other hand, hormones are produced within the body, to be secreted by specific glands. For example, vitamin D in the form called cholecalciferol (D3) is technically a hormone, being synthesized in the skin from the ultraviolet irradiation of 7-dehydrocholesterol, a metabolite or metabolic product of cholesterol. On the other hand, an almost identical form called ergocalciferol (D2) is synthetically prepared by the irradiation of ergesterol from yeast, and is the type used in nutritional supplements and fortified foods. It is therefore a vitamin (and large doses are considered toxic). 

Boyle, M. R, Noschese, M. L., Watts, S. L. et al. 2005. Failure of high-dose ergocalciferol to correct vitamin D deficiency in adults with cystic fibrosis. Am J Respir Crit Care Med 172 212-7. 

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