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Active Vitamin D Analogue (CKD-MBD / Secondary Hyperparathyroidism) Pregnancy: Avoid — calcitriol crosses placenta; hypercalcaemia risk to foetus. Use only with specialist oversight in pregnancy; lowest effective dose if essential.

Calcitriol

Brand names: Rocaltrol, Calcijex (IV)

Adult dose

Dose: 0.25 micrograms once daily (initial oral dose). IV (dialysis): 0.5–3 micrograms three times weekly post-dialysis
Route: Oral (capsules) or Intravenous (dialysis patients)
Frequency: Once daily (oral); three times weekly post-dialysis (IV)
Max: Oral: 1–2 micrograms/day (titrate to PTH response). IV: 3 micrograms per dialysis session
Secondary hyperparathyroidism in CKD stages 3–5D. Oral: start 0.25 micrograms once daily, increase by 0.25 micrograms every 4–8 weeks based on PTH response. IV: given after each dialysis session (3× weekly). Do NOT use if serum calcium >2.55 mmol/L or phosphate >1.8 mmol/L. Source: BNF 90; KDIGO CKD-MBD Guidelines 2017.

Paediatric dose

Dose: 0.01–0.05 micrograms/kg/day (oral). Monitor serum calcium closely — children more sensitive to hypercalcaemia micrograms/day/kg
Route: Oral
Frequency: Once daily
Max: 2 micrograms/day
Renal osteodystrophy in children with CKD. Dose titrated to PTH suppression. Calcium and phosphate monitoring is mandatory. Source: BNF for Children 2024; KDIGO CKD-MBD.

Dose adjustments

Renal

Calcitriol is the active form and does not require renal activation (bypasses 1-alpha-hydroxylase) — this is specifically why it is used in CKD where 1-alpha-hydroxylase activity is deficient. No dose adjustment for renal impairment — dose titrated against PTH and calcium response.

Hepatic

No dose adjustment required — calcitriol is not CYP-metabolised to a clinically significant degree for hepatic dose adjustments.

Paediatric weight-based calculator

Renal osteodystrophy in children with CKD. Dose titrated to PTH suppression. Calcium and phosphate monitoring is mandatory. Source: BNF for Children 2024; KDIGO CKD-MBD.

Clinical pearls

  • Why calcitriol in CKD: failing kidneys lose 1-alpha-hydroxylase activity → cannot convert 25-OH-vitamin D to active calcitriol (1,25-dihydroxyvitamin D3) → low calcitriol → reduced intestinal calcium absorption → hypocalcaemia → secondary hyperparathyroidism → renal osteodystrophy. Calcitriol bypasses the blocked 1-alpha-hydroxylase step completely.
  • PTH target in CKD-MBD: KDIGO 2017 recommends keeping PTH 2–9× ULN for dialysis patients (typically 150–600 pg/mL for dialysis; lower targets for CKD stages 3–5 not on dialysis). Excessive PTH suppression with calcitriol risks adynamic bone disease — a paradoxical complication where bone turnover is too low, increasing fracture risk.
  • Calcium × phosphate product: maintain calcium-phosphate product <4.4 mmol²/L² (or <55 mg²/dL²). Above this threshold, calcium phosphate crystals precipitate in soft tissues, coronary arteries, and cardiac valves — calciphylaxis risk. Always manage hyperphosphataemia with binders BEFORE or alongside calcitriol therapy.
  • Calcimimetics (cinacalcet) vs calcitriol: cinacalcet activates CaSR on parathyroid gland → suppresses PTH synthesis without raising serum calcium. Calcitriol suppresses PTH gene transcription but raises calcium. KDIGO recommends individualising choice — calcitriol used more in CKD stages 3–5; cinacalcet preferred when calcium already elevated. EVOLVE trial showed cinacalcet reduced PTH but did not reduce CV events in dialysis patients.
  • Vitamin D analogue choice: alfacalcidol (1-alpha-hydroxyvitamin D3) requires one-step hepatic conversion to calcitriol — has similar clinical profile. Paricalcitol (selective vitamin D receptor activator) used in dialysis — theoretical advantage of less calcium rise. Calcitriol remains the most widely used active vitamin D in UK CKD. Source: BNF 90; BNF for Children 2024; KDIGO CKD-MBD Guidelines 2017.

Contraindications

  • Hypercalcaemia (serum calcium >2.55 mmol/L — stop until normalised)
  • Vitamin D toxicity
  • Hypercalciuria with renal stone risk
  • Hyperphosphataemia not controlled by phosphate binders (calcitriol increases intestinal phosphate absorption)

Side effects

  • Hypercalcaemia (most important toxicity — nausea, vomiting, confusion, polyuria, constipation, arrhythmia)
  • Hypercalciuria (renal stone risk)
  • Metastatic calcification (calcium × phosphate product >55 mg²/dL²: calcification of soft tissues, vessels, heart)
  • Hyperphosphataemia (increases intestinal phosphate absorption — worsens if phosphate binders inadequate)
  • Oversuppression of PTH (adynamic bone disease risk — PTH below 100 pg/mL in dialysis patients)

Interactions

  • Calcium-containing supplements and phosphate binders: additive hypercalcaemia risk — monitor calcium levels
  • Thiazide diuretics: impair renal calcium excretion → additive hypercalcaemia
  • Digitalis glycosides (digoxin): hypercalcaemia potentiates digoxin toxicity — maintain strict calcium monitoring
  • Cholestyramine and mineral oil: reduce calcitriol absorption — separate by 4 hours
  • Phenytoin and phenobarbitone: CYP3A4 inducers — increase calcitriol catabolism; may need higher doses

Monitoring

  • Serum calcium (monthly initially, then every 3 months when stable — stop if >2.55 mmol/L)
  • Serum phosphate (monthly — ensure controlled before adding calcitriol)
  • PTH (every 3 months in CKD stage 5D; 6-monthly in earlier stages — titrate dose to PTH target)
  • Calcium × phosphate product (monthly)
  • Urinary calcium if oral use in non-dialysis CKD (hypercalciuria → renal stones)

Reference: BNFc; BNF 90; BNF for Children 2024; KDIGO CKD-MBD Clinical Practice Guideline Update 2017; KDIGO CKD Guideline 2024. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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