Ortho DF Disease Interactions

The use of folic acid is contraindicated in patients with undiagnosed anemia. Folic acid in dosages above 1 mg/day can obscure the diagnosis of pernicious anemia by alleviating the hematologic abnormalities while allowing the progression of neurologic complications. In addition, folic acid alone is improper therapy in the treatment of pernicious anemia and other megaloblastic anemias where vitamin B12 is deficient.

Vitamin D analogs function to increase serum calcium concentrations and can exacerbate arrhythmias, particularly in patients receiving cardiac glycosides. Therapy with vitamin D analogs should be administered cautiously in patients with or predisposed to cardiac arrhythmias. Clinical monitoring of serum electrolyte concentrations and cardiac function is recommended.

Vitamin D analogs administered in the presence of hyperphosphatemia can result in precipitation of calcium-phosphate deposits within the vascular or renal systems or other soft tissue calcifications. A solubility product (Serum Calcium X Phosphate) should not exceed 70. Serum electrolyte concentrations should be corrected prior to vitamin D analog therapy and monitored during therapy.

Vitamin D analogs such as calciferol and ergocalciferol should not be given to patients with hypercalcemia, malabsorption syndrome, or evidence of vitamin D toxicity.

Ergocalciferol, cholecalciferol, and calcifediol undergo renal biotransformation during metabolic activation. Renal impairment can alter metabolic and therapeutic activity of certain vitamin D analogs. Alternative vitamin D analogs such as dihydrotachysterol (hepatic activation) and calcitriol (active form) may be considered in patients with compromised renal function.

Vitamin D analogs are fat soluble and oral formulations require bile for adequate intestinal absorption. Hepatic and/or biliary dysfunction decrease the absorption of vitamin D analogs. Metabolites of vitamin D analogs are primarily excreted in bile and feces. Ergocalciferol, cholecalciferol, and dihydrotachysterol undergo hepatic hydroxylation during metabolic activation. Hepatic impairment can alter the metabolic and therapeutic activity of certain vitamin D analogs. Alternative vitamin D analogs such as calcifediol (requires renal activation) and calcitriol (active form) may be considered in patients with compromised hepatic function.