DRISDOL brand of ergocalciferol capsules, USP, is a synthetic calcium regulator for oral administration. Ergocalciferol is a white, colorless crystal, insoluble in water, soluble in organic solvents, and slightly soluble in vegetable oils. It is affected by air and by light. Ergosterol or provitamin D2 is found in plants and yeast and has no antirachitic activity. There are more than 10 substances belonging to a group of steroid compounds, classified as having vitamin D or antirachitic activity. One USP unit of vitamin D2 is equivalent to one International Unit (IU), and 1 mcg of vitamin D2 is equal to 40 IU. Each capsule contains 1.25 mg (50,000 International Units vitamin D) of ergocalciferol, USP, in an edible vegetable oil. Ergocalciferol, also called vitamin D2, is 9, 10-secoergosta-5,7,10 (19), 22-tetraen-3-ol, (3β,5Z,7E,22E)-; (C28H44O) with a molecular weight of 396.65, and has the following structural formula: Inactive Ingredients: FD&C Blue #1, FD&C Yellow #5, Gelatin, Glycerin, Parabens, Soybean Oil.