Vitamin D hormone (calcium/phosphate regulation)
Calcitriol is the active form of vitamin D. It is used to treat calcium deficiency and bone changes in people with kidney disease (including dialysis) and in people with hypoparathyroidism. The dose is adjusted with regular calcium tests.
Also known as: Rocaltrol, calcitriol, 1,25-dihidroxicolecalciferol, alatrofisterol
Calcitriol + loop diuretic: opposing effects on serum calcium.
Calcitriol (active vitamin D) increases intestinal calcium absorption and tends to raise serum calcium, while furosemide increases urinary calcium excretion and tends to lower it. The effects are opposing and, in practice, the combination is sometimes used (for example, in hypercalcaemia with hypercalciuria), but requires monitoring: furosemide can mask calcitriol-induced hypercalcaemia or, in dehydrated patients, precipitate hypocalcaemia. Monitor serum calcium, magnesium and renal function, and adjust doses according to therapeutic goals.
Calcitriol + loop diuretic: opposing effects on serum calcium. Monitor calcium and renal function.
Furosemide increases renal calcium excretion, partially counteracting calcitriol.
Serum calcium on long-term therapy.
Cramps, paraesthesia (hypocalcaemia).
Monitor serum calcium on prolonged combination, especially in renal impairment.
DailyMed (FDA) — approved Calcitriol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8465337c-86ca-ea9d-e053-2991aa0ab167 ; approved Furosemide label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6d9caaab-d874-4cf1-b9fe-408452a18998 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Calcitriol + thiazide: risk of hypercalcaemia (reduced renal calcium excretion).
Thiazides decrease renal calcium excretion (hydrochlorothiazide increases tubular calcium reabsorption) and the hydrochlorothiazide label documents hypercalcaemia and hypophosphataemia in patients on prolonged thiazide therapy, with parathyroid changes; the calcitriol label explicitly states that "thiazides induce hypercalcaemia by reducing urinary calcium excretion" and that there are reports of hypercalcaemia when thiazides are given concomitantly with calcitriol, recommending caution. The combination thus adds up the two hypercalcaemic mechanisms. Monitor serum calcium (and the calcium x phosphorus product), especially at initiation or dose adjustment; watch for hypercalcaemia signs (weakness, headache, nausea, vomiting, constipation, polyuria) and reduce/stop calcitriol or calcium supplements if needed.
Calcitriol + hydrochlorothiazide: thiazides reduce renal calcium excretion and can potentiate calcitriol-induced hypercalcaemia. Monitor serum calcium.
Thiazides reduce urinary calcium excretion, adding to the hypercalcaemic effect of calcitriol.
Serum calcium and renal function periodically.
Polyuria, constipation, confusion, renal stones.
Monitor serum calcium, especially in the first weeks and in renal impairment.
DailyMed (FDA) — approved Calcitriol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8465337c-86ca-ea9d-e053-2991aa0ab167 ; approved Hydrochlorothiazide label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0789baef-3424-43ab-a3fb-4908172da565 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Calcitriol + digoxin: calcitriol-enhanced hypercalcaemia increases the risk of digitalis toxicity.
Calcitriol (active vitamin D) increases intestinal calcium absorption and can raise serum calcium. Hypercalcaemia combined with digoxin increases the risk of arrhythmias, especially in patients with renal impairment or on calcium supplements. Digitalis toxicity can occur at digoxin levels that would be safe with normal serum calcium. Monitor serum calcium during calcitriol treatment (especially with calcium supplementation or kidney disease), watch for digitalis toxicity signs and adjust accordingly.
Calcitriol raises serum calcium and hypercalcaemia increases digitalis toxicity (arrhythmias). Monitor serum calcium and toxicity signs.
Calcitriol increases calcium absorption; hypercalcaemia sensitises the myocardium to digoxin.
Serum calcium, renal function, ECG.
Nausea, arrhythmias, altered colour vision, confusion.
Monitor serum calcium and signs of digoxin toxicity; adjust digoxin dose if needed.
DailyMed (FDA) — approved Calcitriol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8465337c-86ca-ea9d-e053-2991aa0ab167 ; approved Digoxin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e61d2108-d871-44c0-b12a-2e61fbb56967 — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Calcitriol + cholecalciferol: additive vitamin D effect with risk of hypercalcaemia.
Calcitriol (1,25-dihydroxycholecalciferol) is the active form of vitamin D; cholecalciferol (D3) is converted in the body to calcitriol. Concomitant use sums the effects on intestinal calcium absorption and can cause hypercalcaemia, hypercalciuria and, if prolonged, nephrocalcinosis and renal impairment. In patients receiving both (e.g., chronic kidney disease with maintenance D3 and active calcitriol), monitor serum calcium, urinary calcium and renal function, and reduce or stop one form if serum calcium rises above the limit.
Calcitriol + vitamin D3: additive vitamin D effect with risk of hypercalcaemia. Monitor serum calcium.
Both raise serum calcium; the combination may exceed the therapeutic threshold.
Serum calcium (Ca × P).
Symptomatic hypercalcaemia (nausea, confusion, nephrolithiasis).
Avoid the combination unless clinically needed; if used, monitor calcium.
DailyMed (FDA) — approved Calcitriol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=cdcaffc6-e14e-4607-b77b-fc78a8382f60 ; approved Cholecalciferol (vitamin D3) label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3822c324-e22a-4ac4-ac1c-9b63983b516a — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Calcitriol + calcium: additive hypercalcaemia (increased risk of vitamin D toxicity).
Calcitriol increases intestinal calcium absorption; concomitant calcium supplements (carbonate) add to this effect and increase the risk of hypercalcaemia, with anorexia, nausea, constipation, weakness, polyuria and, in severe cases, nephrocalcinosis, arrhythmias and coma. This combination is common and intentional in chronic kidney disease and hypoparathyroidism, but requires monitoring of serum calcium and renal function, adjusting the calcium and calcitriol doses according to the values; also watch the interaction with thiazides, which reduce renal calcium excretion.
Calcium + calcitriol: additive hypercalcaemia. Monitor serum calcium and renal function.
Calcitriol increases intestinal calcium absorption; combined with calcium supplements serum calcium rises.
Serum calcium (Ca × P) and hypercalcaemia symptoms.
Nausea, constipation, weakness, nephrolithiasis.
Monitor serum calcium and phosphate; adjust supplementation.
DailyMed (FDA) — approved Calcitriol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=cdcaffc6-e14e-4607-b77b-fc78a8382f60 ; approved Calcium carbonate label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=348d3dfa-6a52-4583-96e3-83c4bf2df45b — additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Calcium-rich diet adds to calcitriol effect on serum calcium.
Keep calcium intake balanced and monitor serum calcium with concurrent supplementation.
EMC-UK (MHRA) — approved Calcitriol SmPC: https://www.medicines.org.uk/emc/product/101902/smpc
Induced hypercalciuria may favour stone formation.
Monitor serum calcium and urine calcium; ensure adequate hydration.
EMC-UK (MHRA) — approved Calcitriol SmPC: https://www.medicines.org.uk/emc/product/101902/smpc
Calcitriol raises serum calcium and worsens hypercalcaemia.
Contraindicated; stop calcium supplements and monitor serum calcium.
EMC-UK (MHRA) — approved Calcitriol SmPC: https://www.medicines.org.uk/emc/product/101902/smpc
Calcitriol at supraphysiological doses may be teratogenic; at replacement doses the risk is low, monitoring serum calcium.
Use only if necessary, with serum calcium monitoring.
Compatible during breastfeeding at replacement doses, with infant monitoring.
At replacement doses no contraception requirement; caution with high doses.
EMC-UK (MHRA) — approved Calcitriol SmPC: https://www.medicines.org.uk/emc/product/101902/smpc
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Active vitamin D (1,25-dihydroxycholecalciferol): increases intestinal calcium absorption, renal calcium and phosphate reabsorption and bone mobilisation, raising serum calcium and suppressing parathyroid hormone (PTH) secretion. Reduces alkaline phosphatase and the histological manifestations of osteitis fibrosa cystica in renal disease.
Calcitriol acts by binding to the vitamin D receptor (VDR), a nuclear receptor that regulates transcription of genes involved in calcium transport (e.g. intestinal calcium-binding proteins). Unlike native vitamin D, calcitriol does not depend on renal (1-alpha) hydroxylation to become active — hence its efficacy in renal disease.
Oral calcitriol is absorbed in the small intestine. In paediatric patients on peritoneal dialysis (mean dose 10.2 ng/kg), mean Cmax was 116 pmol/L; in patients with nephrotic syndrome peak serum levels were reached at 4 hours and in haemodialysis at 8–12 hours.
Calcitriol is eliminated by metabolic and biliary routes; in renal failure, the elimination half-life increases by at least two-fold compared with healthy subjects. In patients with nephrotic syndrome and haemodialysis, predose and peak serum levels are lower.
Mean serum calcitriol half-life was ~27.4 hours in paediatric patients on peritoneal dialysis; in haemodialysis patients it was estimated at 16.2–21.9 hours and in nephrotic syndrome patients at ~21.9 hours (about twice that of healthy subjects).
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
