calcitriol

General

Pronunciation:
kal-si-trye-ole


Trade Name(s)

  • 1,25–dihydroxycholecalciferol
  • Calcijex
  • Rocaltrol

Ther. Class.
vitamins

Pharm. Class.
fat soluble vitamins

Indications

  • Management of hypocalcemia in patients undergoing chronic renal dialysis (IV and PO).
  • Treatment of hypocalcemia in patients with hypoparathyroidism or pseudohypoparathyroidism (PO only).
  • Management of secondary hyperparathyroidism and resulting metabolic bone disease in predialysis patients with moderate to severe chronic kidney disease (CCr 15–55 mL/min) (PO only).

Unlabeled Use(s):

  • Rickets.
  • Management of hypocalcemia in premature infants.

Action

  • Calcitriol is the active form of vitamin D.
  • Promotes the absorption of calcium and decreases parathyroid hormone concentrations.

Therapeutic Effect(s):

  • Treatment and prevention of deficiency states, particularly bone manifestations.
  • Improved calcium and phosphorous homeostasis in patients with chronic kidney disease.

Pharmacokinetics

Absorption: IV administration results in complete bioavailability; well absorbed following oral administration.

Distribution: Crosses the placenta and enters breast milk.

Protein Binding: 99.9%.

Metabolism and Excretion: Undergoes enterohepatic recycling and is excreted mostly in bile.

Half-life: 5–8 hr (with normal renal function); 16–22 hr (chronic renal failure).

TIME/ACTION PROFILE (effects on serum calcium)

ROUTEONSETPEAKDURATION
PO2–6 hr2–6 hr3–5 days
IVunknownunknownunknown

Contraindication/Precautions

Contraindicated in:

  • Hypersensitivity
  • Hypercalcemia
  • Vitamin D toxicity
  • Concurrent use of magnesium-containing antacids or other vitamin D supplements
  • Lactation: Potential for serious adverse reactions in infant.

Use Cautiously in:

  • Patients receiving digoxin
  • OB:  No adequate, well-controlled studies; use only if benefit outweighs potential risk to fetus.

Adverse Reactions/Side Effects

Seen primarily as manifestations of toxicity (hypercalcemia)

CNS: headache, somnolence, weakness

EENT: conjunctivitis, photophobia, rhinorrhea

CV: arrhythmias, hypertension

GI: abdominal pain, anorexia, constipation, dry mouth, liver function test elevation, metallic taste, nausea, PANCREATITIS, polydipsia, vomiting, weight loss

GU: albuminuria, azotemia, decreased libido, nocturia, polyuria

Derm: pruritus

F and E: hypercalcemia

Local: pain at injection site

Metabolic: hyperthermia

MS: bone pain, metastatic calcification, muscle pain

Misc: allergic reactions (pruritis, rash, urticaria)

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

  •  Cholestyramine,  colestipol, or  mineral oil  ↓ absorption of vitamin D analogues.
  • Use with  thiazide diuretics  may result in hypercalcemia.
  •  Corticosteroids  ↓ effectiveness of vitamin D analogues.
  • Use with  digoxin  ↑ risk of arrhythmias.
  • Concurrent use of  magnesium-containing drugs  may lead to hypermagnesemia.
  •  Calcium-containing drugs  may ↑ risk of hypercalcemia.
  • Concurrent use of other  Vitamin D supplements  (↑ risk of hypercalcemia).

Drug-Food:

Ingestion of foods high in calcium content (see food sources for specific nutrients) may lead to hypercalcemia.

Route/Dosage

Hypocalcemia During Dialysis

PO (Adults): 0.25 mcg/day or every other day; if needed, may ↑ by 0.25 mcg/day at 4–8 wk intervals (typical dosage = 0.5–1 mcg/day).

PO (Children <10 kg): 0.05 mcg every other day; 10–20 kg: 0.1–0.15 mcg daily; >20 kg 0.25 mcg daily.

IV (Adults): 0.5 mcg (0.01 mcg/kg) 3 times weekly during dialysis. May be increased by 0.25–0.5 mcg/dose at 2- to 4-wk intervals (typical maintenance dose = 0.5–3 mcg 3 times weekly (0.01–0.05 mcg/kg 3 times weekly).

IV Children: 0.01–0.05 mcg/kg 3 times weekly during dialysis.

Hypoparathyroidism

PO (Adults and Children ≥6 yr): 0.25 mcg/day initially; if needed, may ↑ dose by 0.25 mcg/day at 2–4 wk intervals (typical dosage = 0.5–2 mcg/day).

PO (Children ≤5 yr): <1 yr– 0.04–0.08 mcg/kg/day 1–5 yr– 0.25–0.75 mcg/day.

Predialysis Patients

PO (Adults and Children ≥3 yr): 0.25 mcg/day; if needed, may ↑ dosage up to 0.5 mcg/day.

Rickets

PO (Adults and Children): Vitamin D-dependent– 1 mcg daily;  Vitamin D-resistant– Inital 0.015–0.02 mcg/kg daily; range: 0.03–0.06 mcg/kg daily; maximum dose: 2 mcg daily.

Hypocalcemia in Premature Infants

PO Neonates: 1 mcg daily for first 5 days of life.

IV Neonates: Tetany– 0.05 mcg/kg daily for 5–12 days.

Availability (generic available)

Capsules: 0.25 mcg, 0.5 mcg

Oral solution: 1 mcg/mL in 15-mL bottle

Injection: 1 mcg/mL in 1-mL ampules

Assessment

  • Assess for symptoms of vitamin deficiency prior to and periodically during therapy.
  • Assess patient for bone pain and weakness prior to and during therapy.
  • Observe patient carefully for evidence of hypocalcemia (paresthesia, muscle twitching, laryngospasm, colic, cardiac arrhythmias, and Chvostek's or Trousseau's sign). Protect symptomatic patient by raising and padding side rails; keep bed in low position.
  • Children: Monitor height and weight; growth arrest may occur in prolonged high-dose therapy.

Lab Test Considerations:

Serum calcium and phosphorus concentrations should be drawn twice weekly during initial therapy. Serum calcium, phosphorus, magnesium, alkaline phosphatase, and intact PTH concentrations should then be monitored at least monthly.

  • The serum calcium times phosphate product (Ca X P) should no exceed 70 mg2 /dL2  (patients may be at ↑ risk of calcification).
  • May cause false ↑ cholesterol levels.

Toxicity Overdose:

Toxicity is manifested as hypercalcemia, hypercalciuria, and hyperphosphatemia. Assess patient for appearance of nausea, vomiting, anorexia, weakness, constipation, headache, bone pain, and metallic taste. Later symptoms include polyuria, polydipsia, photophobia, rhinorrhea, pruritus, and cardiac arrhythmias. Notify physician or other health care professional immediately if these signs of hypervitaminosis D occur. Treatment usually consists of discontinuation of calcitriol, a low-calcium diet, use of low-calcium dialysate in peritoneal dialysis patients, or administration of a laxative. IV hydration and loop diuretics may be ordered to increase urinary excretion of calcium. Hemodialysis may also be used. If patient has hyperphosphatemia, treatment with an oral phosphate-binding agent (e.g. calcium acetate, sevelamer, lanthanum carbonate) may be needed.

Potential Diagnoses

Implementation

  • PO May be administered without regard to meals. Measure solution accurately with calibrated dropper provided by manufacturer. May be mixed with juice, cereal, or food, or dropped directly into mouth. Capsules and solution should be protected from light.
  • PO Liquid may be withdrawn from capsules with a needle and syringe. Both the 0.25 mcg and 0.5 mcg capsules contain 0.17 mL.
  • IV Push:  Administer by rapid injection through the catheter at the end of a hemodialysis period.

Patient/Family Teaching

  • Advise patient to take medication as directed. Take missed doses as soon as remembered that day, unless almost time for next dose; do not double up on doses.
  • Review diet modifications with patient. See food sources for specific nutrients for foods high in calcium and vitamin D. Renal patients must still consider renal failure diet in food selection. Health care professional may order concurrent calcium supplement.
  • Encourage patient to comply with dietary recommendations of health care professional. Explain that the best source of vitamins is a well-balanced diet with foods from the 4 basic food groups and the importance of sunlight exposure. See food sources for specific nutrients for foods high in vitamin D.
  • Patients self-medicating with vitamin supplements should be cautioned not to exceed RDA. The effectiveness of megadoses for treatment of various medical conditions is unproved and may cause side effects.
  • Advise patient to avoid concurrent use of antacids containing magnesium.
  • Review symptoms of overdosage and instruct patient to report these promptly to health care professional.
  • Emphasize the importance of follow-up exams to evaluate progress.

Evaluation/Desired Outcomes

Normalization of serum calcium and parathyroid hormone levels.

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