alfacalcidol

Absorption: Completely absorbed following oral administration.

Distribution: Unknown.

Protein Binding: Extensively to vitamin D–binding protein.

Metabolism/Excretion: Following absorption, 50% is rapidly converted by liver to active metabolite (1,25–(OH)₂D₃; 13% renally excreted.

Half-Life: 3 hr.

Time/Action Profile ⬆ ⬇

(plasma concentrations of active metabolite)

ROUTE	ONSET‡	PEAK	DURATION‡
PO	6 hr	12 hr	few days–1 wk
IV	unknown	4 hr	few days–1 wk

‡Effect on intestinal calcium absorption, bone pain, and muscle weakness improve within 2 wk–3 mo.

‡Effect on serum calcium concentrations following discontinuation.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity,
Lactation: Lactation.

Use Cautiously in:

OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Pedi: Safety and effectiveness not established in children.

Adv. Reactions/Side Effects ⬆ ⬇

CV: ARRHYTHMIAS, hypertension

Derm: pruritus, rash

EENT: conjunctivitis, photophobia

F and E: ↑thirst, hypercalcemia, hyperphosphatemia, hyperthermia, polydipsia

GI: constipation, nausea, anorexia, dry mouth, PANCREATITIS, vomiting

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

Metab: hypercholesterolemia, hyperthermia

MS: arthralgia, myalgia

Neuro: headache, drowsiness, dysgeusia, weakness

Interactions ⬆ ⬇

Drug-drug:

Hypercalcemia ↑ risk of toxicity from digoxin.
↑risk of toxicity with other vitamin D analogs.
Bile acid sequestrants, including cholestyramine, or mineral oil may ↓ absorption and effectiveness.
Barbiturates and other anticonvulsants may ↓ levels and effectiveness; larger doses of alfacalcidol may be required.

Route/Dosage ⬆ ⬇

PO (Adults ): Predialysis patients: 0.25 mcg/day for 2 mo initially; if necessary, ↑ dose by 0.25 mcg/day every 2 mo (usual range 0.5–1 mcg/day); Dialysis patients: 1 mcg/day; if necessary, ↑ dose by 0.5 mcg/day every 2–4 wk (usual range 1–2 mcg/day; max = 3 mcg/day). When normalization occurs, ↓ dose to minimum amount required to maintain normal serum calcium concentrations.
IV (Adults ): Dialysis patients: 1 mcg during each dialysis session (2–3 times weekly); if necessary, ↑ dose weekly by 1 mcg per dialysis session up to 12 mcg/wk (range 1.5–12 mcg/wk). When normalization occurs, ↓ dose to minimum amount required to maintain normal serum calcium concentrations.

Availability ⬆ ⬇

Soft gel capsules: 0.25 mcg; 1 mcg
Oral drops: 2 mcg/mL
Solution for injection (contains ethanol and propylene glycol): 2 mcg/mL

Assessment ⬆ ⬇

Assess for signs of vitamin D deficiency before and during treatment.
Assess for bone pain and weakness during therapy; usually ↓ within 2 wk to 3 mo.

Lab Test Considerations:

For predialysis patients: Monitor serum calcium and phosphate concentrations monthly and electrolytes periodically during treatment. For dialysis patients: Monitor serum calcium at least twice weekly during dose titration. If hypercalcemia occurs, ↓ dose of alfacalcidol by 50% and stop all calcium supplements until calcium concentrations return to normal. May ↑ plasma phosphorous concentrations. Maintain serum phosphate concentrations <2 mmol/L. Monitor inorganic phosphorus, magnesium, alkaline phosphatase, serum creatinine, BUN, 24-hr urinary calcium, and protein as needed.

Toxicity and Overdose:

Toxicity is manifested as hypercalcemia, hypercalciuria, and hyperphosphatemia. Assess 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 provider immediately if these signs/symptoms of hypervitaminosis D occur. Treatment usually consists of discontinuation of alfacalcidol, a low-calcium diet, and stopping calcium supplements. Persistent or markedly ↑ serum calcium concentrations in dialysis patients may be corrected by dialysis against a calcium-free dialysate.

Implementation ⬆ ⬇

PO: Administer with food. Swallow capsules whole; do not divide. Use calibrated dropper with oral solution for accurate dose. Oral solution may be mixed with water or milk.
IV: Administer IV during hemodialysis. Shake well before use. Keep refrigerated. Single use vials; discard unused portion.

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication to patient. Advise patient to read Patient Information before starting therapy. Advise patient to take medication as directed. Do not stop taking without consulting with health care provider. If dose is missed, take missed dose as soon as possible. If it is almost time for the next dose, skip dose and administer on regular schedule. Do not double the dose.
Advise patient to notify health care provider of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care provider before taking other medications.
Advise patient and family/caregiver to notify health care provider if signs/symptoms of hypercalcemia occur.
Review diet modifications with patient. See Food Sources for Specific Nutrients for foods high in calcium and vitamin D. Patients with kidney disease must still consider renal failure diet in food selection. Health care provider may order concurrent calcium supplement.
Encourage patient to comply with dietary recommendations. Explain that best source of vitamins is a well-balanced diet with foods from all four basic food groups and sunlight exposure for vitamin D.
Advise patient to avoid concurrent use of antacids containing magnesium during therapy.
Rep: Advise women of reproductive potential to notify health care provider if pregnancy is planned or suspected or if breastfeeding.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇