Calcitriol

Calcitriol

[capsules 13 cents; liquid $3.94/ml]

ADMINISTRATION ROUTES:

  • PO, NG

ALTERNATIVE NAMES:

  • Rocaltrol

ICU INDICATIONS:

  1. post-menopausal osteoporosis
  2. renal osteodystrophy
  3. secondary hyperparathyroidism
  4. hypoparathyroidism
  5. prevention of corticosteroid-induced osteoporosis

    Note: initiation of calcitriol in ICU is rarely indicated and this therapy is often withheld while patients are critically ill (see PRECAUTIONS).

PRESENTATION AND ADMINISTRATION:

  • PO / NG:
    Calcitriol-AFT 0.25mcg capsules (orange) Rocaltrol solution 1mcg/ml (colourless to slightly yellowish oily solution). Mix with a drink (eg orange juice). Liquid is available if NG administration is deemed necessary

DOSAGE:

  • The optimal daily dose of calcitriol must be carefully determined for each patient. Calcitriol can be administered orally either as a capsule or as an oral solution. Calcitriol therapy should always be started at the lowest possible dose and should not be increased without careful monitoring of serum calcium.
  • PO:
    0.25mcg per day; increasing to up to 0.5mcg twice daily if required.

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

  • Dose as in normal renal function

DOSAGE IN PAEDIATRICS:

  • PO:
    0.02mcg/kg daily oral, increase by 0.02mcg/kg every 4-8 weeks according to serum calcium (usual maximum 0.1mcg/kg)

CLINICAL PHARMACOLOGY:

  • Calcitriol is a synthetic vitamin D analog which is active in the regulation of the absorption of calcium from the gastrointestinal tract and its utilization in the body.

CONTRAINDICATIONS:

  1. hypercalcemia
  2. evidence of vitamin D toxicity
  3. known hypersensitivity to calcitriol

WARNINGS

  • Calcitriol is the most potent metabolite of vitamin D available. Excessive dosing can cause hypercalcemia, hypercalciuria, and hyperphosphatemia.
  • Calcitriol increases inorganic phosphate levels in serum. While this is desirable in patients with hypophosphatemia, caution is called for in patients with renal failure because of the danger of ectopic calcification. A non-aluminum phosphate-binding compound and a low-phosphate diet should be used to control serum phosphorus levels in patients undergoing dialysis.

PRECAUTIONS

  • General:
    Excessive dosage of calcitriol induces hypercalcemia. Should hypercalcemia develop, treatment with calcitriol should be stopped immediately. Immobilised patients, e.g., the critically ill, are particularly exposed to the risk of hypercalcemia which is why this medication is often withheld in ICU.
  • Laboratory Tests:
    No tests in addition to routine ICU tests are required
  • Drug/Laboratory Test Interactions:
    None known

IMPORTANT DRUG INTERACTIONS FOR THE ICU

  • Thiazides
    Thiazides are known to induce hypercalcemia by the reduction of calcium excretion in urine. Some reports have shown that the concomitant administration of thiazides with calcitriol causes hypercalcemia. Therefore, precaution should be taken when coadministration is necessary.
  • Digitalis
    Calcitriol dosage must be determined with care in patients undergoing treatment with digitalis, as hypercalcemia in such patients may precipitate cardiac arrhythmias.

ADVERSE REACTIONS

  • Since calcitriol is believed to be the active hormone which exerts vitamin D activity in the body, adverse effects are, in general, similar to those encountered with excessive vitamin D intake, i.e., hypercalcemia syndrome or calcium intoxication (depending on the severity and duration of hypercalcemia) (see WARNINGS).
  • The early and late signs and symptoms of vitamin D intoxication associated with hypercalcemia include:
    Early:
    Weakness, headache, somnolence, nausea, vomiting, dry mouth, constipation, muscle pain, bone pain, metallic taste, and anorexia.
    Late:
    Polyuria, polydipsia, anorexia, weight loss, nocturia, conjunctivitis (calcific), pancreatitis, photophobia, rhinorrhea, pruritus, hyperthermia, decreased libido, elevated Cr, albuminuria, hypercholesterolemia, elevated AST and ALT, ectopic calcification, nephrocalcinosis, hypertension, cardiac arrhythmias, dystrophy, sensory disturbances, dehydration, apathy, arrested growth, urinary tract infections, and, rarely, overt psychosis.

Critical Care Drug Manual

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