warnings
WARNINGS Overdosage of any form of vitamin D, including doxercalciferol, is dangerous (see OVERDOSAGE ). Progressive hypercalcemia due to overdosage of vitamin D and its metabolites may be so severe as to require emergency attention. Acute hypercalcemia may exacerbate tendencies for cardiac arrhythmias and seizures and may potentiate the action of digitalis drugs. Chronic hypercalcemia can lead to generalized vascular calcification and other soft-tissue calcification. The serum calcium times serum phosphorus (Ca X P) product should be maintained at <55 mg 2 /dL 2 in patients with chronic kidney disease. Radiographic evaluation of suspect anatomical regions may be useful in the early detection of this condition. Since doxercalciferol is a precursor for 1α,25-(OH) 2 D 2 , a potent metabolite of vitamin D 2 , pharmacologic doses of vitamin D and its derivatives should be withheld during doxercalciferol treatment to avoid possible additive effects and hypercalcemia. Oral calcium-based or other non-aluminum-containing phosphate binders and a low phosphate diet should be used to control serum phosphorus levels in patients with chronic kidney disease. Uncontrolled serum phosphorus exacerbates secondary hyperparathyroidism and can lessen the effectiveness of doxercalciferol in reducing blood PTH levels. If hypercalcemia occurs after initiating doxercalciferol therapy, the dose of doxercalciferol and/or calcium-containing phosphate binders should be decreased. If hyperphosphatemia occurs after initiating doxercalciferol therapy, the dose of doxercalciferol should be decreased and/or the dose of phosphate binders increased. (See dosing recommendations for doxercalciferol under DOSAGE AND ADMINISTRATION section.) Magnesium-containing antacids and doxercalciferol should not be used concomitantly in patients on chronic renal dialysis because such use may lead to the development of hypermagnesemia.