Calcitriol
Vitamins
Vitamins
The active form of vitamin D (1,25-dihydroxyvitamin D3). It works without kidney activation, so it is used in chronic kidney disease.
Quick facts
- Group
- Vitamins
- Target
- Vitamin D receptor (VDR), a nuclear receptor
- Used for
- Secondary hyperparathyroidism
- Key effects
- Early signs of hypercalcaemia · Muscle or bone pain
- Monitor
- Serum calcium · Phosphate
- ATC
- A11CC04
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows calcitriol itself bound to the ligand-binding domain of the human vitamin D receptor.
Calcitriol is the hormone normally made by the kidney from vitamin D3. It binds the vitamin D receptor in the gut, bone, kidney and parathyroid glands, increases calcium absorption and suppresses parathyroid hormone. In kidney failure the kidney cannot make enough calcitriol, which causes hypocalcaemia and secondary hyperparathyroidism; giving calcitriol bypasses that step.
- Calcitriol needs no liver or kidney activation
- It binds the vitamin D receptor directly
- More calcium absorbed in the gut
- Parathyroid hormone falls
Indications
- Secondary hyperparathyroidism and bone disease in chronic kidney disease before dialysis CKD-mineral and bone disorder (renal osteodystrophy) →
- Hypocalcaemia and bone disease in patients on chronic dialysis Chronic kidney disease →
- Hypocalcaemia in hypoparathyroidism and pseudohypoparathyroidism Hypoparathyroidism (incl. post-thyroidectomy hypocalcaemia) →
Adverse effects
Common
- Early signs of hypercalcaemia: weakness, headache, nausea, constipation, dry mouth, metallic taste
- Muscle or bone pain
- Rash, itching or hives (rare)
Contraindications
- Hypercalcaemia
- Vitamin D toxicity
- Hypersensitivity to calcitriol or related drugs
Key interactions
- Digoxin and other digitalis glycosides
- Hypercalcaemia can trigger arrhythmias
- Thiazide diuretics
- Higher risk of hypercalcaemia
- Magnesium-containing antacids
- Hypermagnesaemia in dialysis patients
- Colestyramine; phenytoin or phenobarbital; corticosteroids
- Less calcitriol absorbed (colestyramine), lower levels (enzyme inducers) or opposite effect (corticosteroids)
What is monitored
- Serum calcium, often while the dose is being adjusted, then regularly
- Phosphate, magnesium and alkaline phosphatase
- Parathyroid hormone and creatinine in kidney disease before dialysis
Administration and safety
- Other vitamin D products and calcium supplements are reviewed to avoid stacking.
- Dialysis patients usually follow a low-phosphate diet and may need phosphate binders.
- Magnesium-containing antacids and laxatives are avoided in dialysis.
Pregnancy and breastfeeding
It was teratogenic in rabbits and human data are lacking; it is used only if the benefit justifies the risk. Breastfeeding is avoided.
Nursing care
- Check calcium results before giving it, and report a high value.
- Teach the signs of hypercalcaemia and to report palpitations.
- Ask about digoxin, thiazides and magnesium antacids.
- Advise against breastfeeding while taking it.
Pharmacokinetics
- Absorption
- Absorbed quickly from the gut, with peak levels in about 3–6 hours
- Distribution
- Almost completely bound to plasma proteins
- Elimination
- Metabolites leave mainly in the faeces
- Half-life
- About 5–8 hours in healthy people, at least twice as long in kidney failure; the effect lasts about 3–5 days
Test yourself
Think of the answer, then tap the question to see it.
Why is calcitriol, not colecalciferol, used in advanced kidney disease?
The failing kidney cannot perform 1α-hydroxylation; calcitriol is already active.
What is the main toxicity of calcitriol?
Hypercalcaemia, with hypercalciuria and hyperphosphataemia.
Which heart drug becomes dangerous if calcitriol raises calcium?
Digoxin (digitalis): hypercalcaemia can trigger arrhythmias.
Connections
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - CALCITRIOL capsule (DailyMed (U.S. National Library of Medicine), 2024); Calcitriol: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); RCSB PDB - 1DB1: CRYSTAL STRUCTURE OF THE NUCLEAR RECEPTOR FOR VITAMIN D COMPLEXED TO VITAMIN D (RCSB Protein Data Bank, 2026).
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Representative model, for educational purposes only.