alfacalcidol

Absorption: Completely absorbed following oral administration.

Distribution: Unknown.

Protein Binding: Extensively protein bound.

Metabolism/Excretion: Following absorption, 50% is rapidly converted by liver to active metabolite (1.25–(OH)₂D; 13% renally excreted.

Half-Life: 3 hr.

Time/Action Profile ⬆ ⬇

(levels 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 levels following discontinuation.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Concurrent use of other vitamin D analogs or magnesium-containing antacids;
Lactation: Avoid breastfeeding.

Use Cautiously in:

OB: Potential benefits should be weighed against hazards to fetus and mother;
Pedi: Safety and effectiveness not established.

Adv. Reactions/Side Effects ⬆ ⬇

CNS: headache, drowsiness, weakness

CV: ARRHYTHMIAS, hypertension

EENT: conjunctivitis, photophobia

GI: constipation, nausea, anorexia, dry mouth, metallic taste, pancreatitis, polydipsia, vomiting

Derm: pruritus, rash

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

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

Metab: ectopic calcification, hypercholesterolemia, hyperthermia

MS: bone pain, muscle pain

Interactions ⬆ ⬇

Drug-drug:

Hypercalcemia ↑ risk of toxicity from digoxin.
↑risk of toxicity and adverse reactions with concurrent use of other vitamin D analogs.
Concurrent use of bile acid sequestrants, including cholestyramine, or mineral oil↓ absorption and effectiveness.
Concurrent use of barbiturates and other anticonvulsants may ↓ effectiveness; larger doses of alfacalcidol may be required.

Route/Dosage ⬆ ⬇

PO (Adults ): Pre-dialysis patients: 0.25 mcg/day for 2 mo initially; if necessary, dose increments of 0.25 mg/day may be made at 2 mo intervals (usual range 0.5–1.0 mcg/day); dialysis patients: 1 mcg/day, if necessary dose increments of 0.5 mcg/day may be made at 2–4 wk intervals (usual range 1–2 mcg/day, up to 3 mcg/day). When normalization occurs, dose should be ↓ to minimum amount required to maintain normal serum calcium levels.
IV (Adults ): Dialysis patients: 1 mcg during each dialysis session (2–3 times weekly); if necessary, dose may be ↑ weekly by 1 mcg per dialysis session up to 12 mcg/wk (range 1.5–12 mcg/wk). When normalization occurs, dose should be ↓ to minimum amount required to maintain normal serum calcium levels.

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 prior to and during treatment.
Assess for bone pain and weakness during therapy; usually decreases within 2 wk to 3 mo.

Lab Test Considerations:

For pre-dialysis patients: Monitor serum calcium and phosphate levels monthly and electrolytes periodically during treatment. For dialysis patients: Monitor serum calcium at least twice weekly during dose titration. If hypercalcemia occurs decrease dose of alfacalcidol by 50% and stop all calcium supplements until calcium levels return to normal. May cause ↑ plasma phosphorous levels. Maintain serum phosphate levels <2.0 mmol/L. Monitor inorganic phosphorus, magnesium, alkaline phosphatase, 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 professional immediately if these signs of hypervitaminosis D occur. Treatment usually consists of discontinuation of alfacalcidol, a low-calcium diet, stopping calcium supplements. Persistent or markedly elevated serum calcium levels in hemodialysis patients may be corrected by dialysis against a calcium-free dialysate.

Implementation ⬆ ⬇

PO: Administer with food. Use calibrated dropper with oral 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 ⬆ ⬇

Advise patient to take medication as directed. Do not stop taking without consulting with health care professional.
Advise patient and family to notify health care professional if signs and symptoms of hypercalcemia occur.
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. Explain that best source of vitamins is a well-balanced diet with foods from all 4 basic food groups, and sunlight exposure for vitamin D.
Advise patient to avoid concurrent use of antacids containing magnesium during therapy.
Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care professional before taking any other Rx, OTC, or herbal products.
Rep: Advise females of reproductive potential to notify health care professional 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 ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇