ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Active Vitamin D Analogue Pregnancy: Use with caution — hypercalcaemia risk in pregnancy. Seek specialist advice; monitor calcium closely.

Alfacalcidol (1-alpha-Hydroxycholecalciferol)

Brand names: One-Alpha, Alfacal

Adult dose

Dose: Renal osteodystrophy / CKD stage 4–5: 250–500 nanograms (0.25–0.5 micrograms) OD initially; adjust by 250 nanograms every 2–4 weeks based on calcium level; usual maintenance 0.5–1 microgram OD. Hypoparathyroidism: 0.5–1 microgram OD, adjusted to calcium response (target calcium 2.0–2.25 mmol/L). Osteoporosis with established deficiency: 0.25–1 microgram OD.
Route: Oral (capsule or drops)
Frequency: Once daily
Max: 3 micrograms OD (rarely needed — specialist supervision)
Alfacalcidol requires only hepatic 25-hydroxylation to become active (calcitriol) — bypasses the defective renal 1-hydroxylation in CKD. Much more potent than colecalciferol — hypercalcaemia risk is greater. Monitor calcium closely, especially when initiating or adjusting dose.

Paediatric dose

Dose: 0.05 micrograms/kg
Route: Oral
Frequency: Once daily
Max: 1 microgram OD
BNFc: Neonates to 12 years: 0.05 micrograms/kg OD (max 1 microgram). >12 years: 0.25–1 microgram OD, adjusted per calcium. Seek specialist paediatric renal/endocrinology opinion.

Dose adjustments

Renal

Preferred vitamin D in CKD stages 4–5 and dialysis — bypasses impaired renal activation. Monitor calcium closely (2–4 weekly initially).

Hepatic

Severe hepatic impairment: impaired hepatic hydroxylation — use calcitriol (fully active form) instead.

Paediatric weight-based calculator

BNFc: Neonates to 12 years: 0.05 micrograms/kg OD (max 1 microgram). >12 years: 0.25–1 microgram OD, adjusted per calcium. Seek specialist paediatric renal/endocrinology opinion.

Clinical pearls

  • Critical distinction: colecalciferol (D3) needs TWO activation steps (liver + kidney); alfacalcidol needs only ONE (liver) — hence alfacalcidol/calcitriol are used when kidneys are non-functional
  • Hypercalcaemia with alfacalcidol: withhold dose and ensure adequate hydration — calcium normalises within days (short half-life compared to colecalciferol)
  • Target calcium in hypoparathyroidism: 2.0–2.25 mmol/L (slightly below normal to minimise renal calcification risk)
  • Renal patients on alfacalcidol + calcium carbonate (phosphate binder): monitor both calcium AND phosphate regularly

Contraindications

  • Hypercalcaemia
  • Metastatic calcification
  • Hypersensitivity to alfacalcidol

Side effects

  • Hypercalcaemia (dose-related — most important side effect)
  • Hypercalciuria
  • Pruritus (in renal patients, improvement of uraemic pruritus may occur but hypercalcaemia can worsen)
  • Nausea, constipation

Interactions

  • Calcium supplements — additive hypercalcaemia; monitor closely
  • Thiazide diuretics — additive hypercalcaemia
  • Digoxin — hypercalcaemia potentiates toxicity; monitor closely
  • Cholestyramine, sucralfate — reduce absorption

Monitoring

  • Serum calcium (every 2 weeks initially, then monthly when stable)
  • Serum phosphate
  • 24-hour urinary calcium (long-term)
  • eGFR
  • PTH levels (in secondary hyperparathyroidism)

Reference: BNFc; BNF 90; NICE CG182 (CKD); KDIGO CKD-MBD Guidelines 2017. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways