LETTER TO THE EDITOR – OCTOBER 2000

In a recent article you described the treatment of muscle myopathies with large doses of vitamin D2 (ergocalciferol). What is vitamin-D2 and would 50,000 units all at once not be toxic?

AMC, Canada

Editor: Ergocalciferol also known as vitamin-D2 is produced by ultraviolet radiation of the yeast sterol ergosterol. Cholecalciferol also known as vitamin-D3 is produced in the skin of mammals (including humans) by sun exposure of the precursor 7-dehydrocholesterol. Vitamin D3 is also found in fish liver oils. Both vitamins D2 and D3 are converted in the body to 1,25- dihydroxyvitamin D which is the biologically active form of vitamin D. Vitamin- D in doses of 10,000 IU or more can be toxic if ingested daily for prolonged periods of time. However, the patients in question were treated with 50,000 IU once a week for 6 weeks which would not be in the toxic range. High-dose supplementation (50,000 IU/week) should be done under the supervision of a health care provider as there could be side effects.