calcitriol (systemic)

REMS

Hypocalcemia in patients undergoing chronic renal dialysis.
Hypocalcemia in patients with hypoparathyroidism or pseudohypoparathyroidism.
Secondary hyperparathyroidism and resulting metabolic bone disease in predialysis patients with moderate to severe chronic kidney disease.

Unlabeled Use:

Rickets.
Hypocalcemia in premature infants.

Action ⬆ ⬇

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

Therapeutic effects:

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

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration.

Distribution: Crosses the placenta and enters breast milk.

Protein Binding: 99.9%.

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

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

Time/Action Profile ⬆ ⬇

(effects on serum calcium)

ROUTE	ONSET	PEAK	DURATION
PO	2–6 hr	2–6 hr	3–5 days

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Hypercalcemia;
Vitamin D toxicity;
Concurrent use of magnesium-containing antacids or other vitamin D supplements;
Lactation: Lactation.

Use Cautiously in:

OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk.

Adv. Reactions/Side Effects ⬆ ⬇

Seen primarily as manifestations of toxicity (hypercalcemia)

CV: arrhythmias, hypertension

Derm: pruritus

EENT: conjunctivitis, photophobia, rhinorrhea

F and E: hypercalcemia

GI: abdominal pain, anorexia, constipation, dry mouth, ↑liver enzymes, metallic taste, nausea, PANCREATITIS, polydipsia, vomiting

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

Local: pain at injection site

Metab: hyperthermia, ↓weight

MS: bone pain, metastatic calcification, muscle pain

Neuro: headache, somnolence, weakness

Misc: hypersensitivity reactions

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.

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/day1–5 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: Initial 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.

Availability ⬆ ⬇

(Generic available)

Capsules: 0.25 mcg; 0.5 mcg
Oral solution: 1 mcg/mL

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:

Evaluate serum calcium and phosphorus concentrations twice weekly during initial therapy. Monitor serum calcium, phosphorus, magnesium, alkaline phosphatase, and intact PTH concentrations at least monthly thereafter.
- The serum calcium times phosphate product (Ca * P) should not exceed 70 (patients may be at ↑ risk of calcification).
- May cause false ↑ cholesterol levels.

Toxicity and 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 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.

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.

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. Explain that the best source of vitamins is a well-balanced diet with foods from the 4 basic food groups, as well as the importance of sunlight exposure.
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 notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
Advise patient to avoid concurrent use of antacids containing magnesium.
Review symptoms of overdose and instruct patient to report these promptly to health care professional.
Rep: Advise females of reproductive potential to notify health care professionals if pregnancy is planned or suspected or if breastfeeding.
Emphasize the importance of follow-up exams to evaluate progress.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇