What is the recommended dosage of calcitriol (Vitamin D3) for various conditions?

Calcitriol Dosing by Clinical Indication

Chronic Kidney Disease (Pre-Dialysis)

For adults and children ≥3 years with CKD stages 3-4, start calcitriol at 0.25 mcg/day orally when intact PTH exceeds 70 pg/mL and serum calcium is <10.2 mg/dL. 1, 2

• Initiate therapy when GFR is 15-60 mL/min/1.73 m² to prevent progression to severe bone disease 1
• For children <3 years, use 10-15 ng/kg/day as the starting dose 2
• Increase to 0.5 mcg/day if PTH suppression is inadequate after 2-4 weeks 2
• Target PTH range is 150-300 pg/mL in this population 3
• Check serum calcium and phosphorus twice weekly during the first month, then monthly for 3 months 1, 3

Critical Safety Thresholds

• Absolute contraindication: serum calcium >10.2-10.5 mg/dL 1
• Hold therapy immediately if hypercalcemia develops and restart at 50% of prior dose once calcium normalizes 3
• Ensure adequate but not excessive calcium intake (600-1200 mg/day) 2

Hemodialysis Patients

For dialysis patients with secondary hyperparathyroidism (PTH >300 pg/mL), start calcitriol at 0.25 mcg/day orally or 0.5-1.0 mcg three times weekly intravenously. 4, 2

• Most hemodialysis patients respond to oral doses between 0.5-1.0 mcg/day 2
• Increase by 0.25 mcg/day at 4-8 week intervals if biochemical response is inadequate 2
• For severe hyperparathyroidism (PTH >1200 pg/mL), intravenous dosing is more effective than oral administration 4, 5
• In severe cases, doses up to 3-4 mcg three times weekly IV may be necessary, adjusted based on PTH levels 5
• Target PTH range is 150-300 pg/mL 1, 3

Dosing Frequency Considerations

• Intravenous calcitriol three times weekly is superior to daily oral dosing for PTH suppression in dialysis patients 4
• When using oral therapy, dividing the weekly dose into 2-3 administrations is more effective than once-weekly dosing 6
• Single evening dosing may reduce hypercalciuria risk 4

Monitoring in Dialysis

• Check calcium and phosphorus twice weekly during dose titration 2
• Monitor PTH monthly until stable, then every 3 months 3
• Hold calcitriol if PTH falls below 150 pg/mL and resume at 50% dose when PTH rises above target 3

X-Linked Hypophosphatemia (XLH)

For children with XLH, start calcitriol at 20-30 ng/kg/day divided into 1-2 doses, given in combination with oral phosphate supplements. 4, 1

• Calcitriol requirements are higher during early childhood and puberty 4
• Adjust dose based on serum alkaline phosphatase, PTH, and urinary calcium excretion 4
• Give as single evening dose or divided twice daily; alfacalcidol (if used) should be once daily due to longer half-life 4
• Monitor for hypercalciuria and nephrocalcinosis, which occur in 30-70% of treated patients 4
• Target is to maintain PTH in normal range (10-65 pg/mL) while avoiding hypercalciuria 4

XLH-Specific Precautions

• Do not give phosphate supplements with calcium-containing foods or supplements as this reduces absorption 4
• Large calcitriol doses promote growth but increase nephrocalcinosis risk 4
• Insufficient dosing leads to persistent rickets, high alkaline phosphatase, and secondary hyperparathyroidism 4

Hypoparathyroidism

For hypoparathyroidism, start calcitriol at 0.25 mcg/day in the morning for adults and children ≥6 years. 2

• Most adults and children ≥6 years respond to 0.5-2.0 mcg/day 2
• Children ages 1-5 years typically require 0.25-0.75 mcg/day 2
• Increase dose at 2-4 week intervals if response is inadequate 2
• Check calcium twice weekly during titration 2
• Monitor 24-hour urinary calcium periodically as malabsorption may necessitate higher doses 2

Comparative Efficacy: Calcitriol vs. Paricalcitol

• Both agents achieve similar PTH suppression (-46% with calcitriol vs. -52% with paricalcitol) in CKD stages 3-4 7
• Paricalcitol reaches 40% PTH reduction faster (median 8 vs. 12 weeks) with lower pill burden 7
• Hypercalcemia rates are very low with both agents when properly dosed (3% vs. 2%) 7
• Both cause small increases in calcium and phosphorus (0.3-0.4 mg/dL) 7

Key Dosing Principles Across All Indications

• Always start at the lowest dose and titrate based on biochemical response 2
• Discontinue immediately if hypercalcemia develops 2
• Ensure adequate vitamin D stores (25-OH vitamin D >30 ng/mL) before initiating calcitriol 1
• Address hyperphosphatemia before or concurrent with calcitriol therapy 3
• When resuming after holding for hypercalcemia or oversuppression, restart at 50% of previous dose 3