Drug General Information (ID: DDINP4BWLY)
  Drug Name Ergocalciferol Drug Info Dihydrotachysterol Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Vitamins Antihypoparathyroid Agents
  Structure

 Mechanism of Ergocalciferol-Dihydrotachysterol Interaction (Severity Level: Major)
     Increased risk of hypercalcemia Click to Show/Hide Mechanism Graph
      Drug Name Ergocalciferol Dihydrotachysterol
      Mechanism Hypercalcemia Hypercalcemia
      Key Mechanism Factor 1
Factor Name Hypercalcemia
Factor Description Hypercalcemia is a condition in which the calcium level in your blood is above normal. Too much calcium in your blood can weaken your bones, create kidney stones, and interfere with how your heart and brain work.
      Mechanism Description
  • Increased risk of hypercalcemia by the combination of Ergocalciferol and Dihydrotachysterol 

Recommended Action
      Management Vitamin D analogs should not be used in combination with each other or with pharmacologic doses of vitamin D. Serum calcium and phosphorus levels must be closely monitored during therapy with a vitamin D analog, especially early in treatment during dosage adjustment. The serum calcium X phosphorus product should be maintained at less than 55 in patients with chronic kidney disease and should not be allowed to exceed 70 in any patient. An estimate of daily dietary calcium intake should be made and the intake adjusted when indicated. Patients should be advised to avoid an abrupt increase in dietary calcium intake, as it may trigger hypercalcemia, and to contact their physician if they experience early symptoms of vitamin D intoxication associated with hypercalcemia such as weakness, fatigue, headache, somnolence, vertigo, tinnitus, anorexia, nausea, vomiting, constipation, dry mouth, metallic taste, muscle pain, bone pain, ataxia, and hypotonia. Late symptoms may include polyuria, polydipsia, weight loss, nocturia, conjunctivitis, photophobia, rhinorrhea, pruritus, hyperthermia, decreased libido, and cardiac arrhythmias. Radiographic evaluation of suspect anatomical regions may be useful in the early detection of hypercalcemia. If hypercalcemia develops, treatment with vitamin D and any calcium product should be stopped immediately.

References
1 Cerner Multum, Inc. "UK Summary of Product Characteristics.".
2 Product Information. Hectorol (doxercalciferol). Genzyme Corporation, Cambridge, MA.
3 Product Information. One-Alpha (alfacalcidol). Pharmel Inc, Montreal, IN.