What is Calcitriol (Vitamin D3) 0.25mg?

Calcitriol 0.25mg: Active Vitamin D Metabolite

Calcitriol 0.25mg is the active form of vitamin D (1,25-dihydroxyvitamin D3), which is the most physiologically potent metabolite of vitamin D used to treat conditions requiring direct vitamin D hormone activity, particularly in patients with impaired vitamin D activation. 1

Pharmacology and Description

• Calcitriol is a synthetic form of the active vitamin D metabolite (1,25-dihydroxycholecalciferol or 1,25-dihydroxyvitamin D3), which is normally produced by sequential hydroxylation of vitamin D in the liver and kidneys 1
• Available in 0.25mcg and 0.5mcg oral capsules, as well as 1mcg/mL oral solution 1
• Calcitriol bypasses the need for renal 1α-hydroxylation, making it effective even in patients with kidney dysfunction 2
• Functions by binding to vitamin D receptors, which inhibits keratinocyte proliferation and enhances keratinocyte differentiation 2

Clinical Indications

Chronic Kidney Disease

• Indicated for patients with chronic kidney disease (CKD) on dialysis with serum intact PTH levels >300 pg/mL to reduce PTH to a target range of 150-300 pg/mL 2
• For peritoneal dialysis patients, oral doses of calcitriol 0.5 to 1.0 μg can be given 2-3 times weekly, or a lower dose of 0.25 μg can be administered daily 2
• Intermittent intravenous administration is more effective than daily oral calcitriol in lowering serum PTH levels in hemodialysis patients 2

Secondary Hyperparathyroidism

• Effectively suppresses PTH in CKD patients (achieving approximately 46-52% reduction) 3
• May be considered in patients with corrected serum calcium and/or phosphorus levels above target range 2

Osteoporosis

• Used in the treatment of postmenopausal osteoporosis, showing a significant 3-fold lower rate of new vertebral fractures after 3 years compared to calcium supplementation alone 4
• Typical dosage for osteoporosis is 0.25 μg twice daily 4

Psoriasis

• Calcitriol ointment has shown comparable efficacy to betamethasone dipropionate 0.05% ointment in plaque psoriasis treatment 2
• Better tolerated in readily irritated areas including face, hairline, and flexural areas compared to other vitamin D analogs 2

Monitoring and Safety Considerations

• When initiating therapy, monitor:

  • Serum calcium and phosphorus at least every 2 weeks for first month, then monthly 2
  • Plasma PTH monthly for at least 3 months, then every 3 months once target levels achieved 2

• Dosage adjustments should be made based on:

  • If PTH falls below target range: hold therapy until PTH rises above target, then resume at half dose 2
  • If serum corrected calcium exceeds 9.5 mg/dL: hold therapy until calcium normalizes, then resume at half dose 2
  • If serum phosphorus rises above 4.6 mg/dL: hold therapy, adjust phosphate binders, then resume prior dose when phosphorus normalizes 2

• Management should integrate changes in serum calcium, phosphorus, and plasma PTH levels 2

Adverse Effects and Precautions

• Primary concern is hypercalcemia, though clinical trials show this is infrequent and generally mild at recommended dosages 4
• Requires careful supervision with periodic monitoring of serum calcium and creatinine levels due to narrow therapeutic window 4
• May cause reversible elevation of serum calcium, more likely with doses exceeding 100 g/week 2
• Can increase intestinal absorption of calcium and phosphorus, potentially leading to hypercalcemia and hyperphosphatemia 2

Comparison with Other Vitamin D Formulations

• Unlike cholecalciferol or ergocalciferol (nutritional vitamin D), calcitriol does not require kidney activation 5
• Compared to paricalcitol in CKD patients, both agents effectively suppress PTH, though paricalcitol may achieve target reduction faster (8 vs 12 weeks) 3
• Some dialysis patients may benefit from combination therapy with both cholecalciferol and calcitriol to address both vitamin D deficiency and calcitriol hormone insufficiency 6
• Alfacalcidol requires 25-hydroxylation to become active, whereas calcitriol is already the active form 5

Special Considerations

• Pregnancy category C medication 2
• In patients already on active vitamin D therapy, monitoring 25-hydroxyvitamin D levels and supplementing if deficient is recommended 7
• If serum corrected total calcium exceeds 10.2 mg/dL, all forms of vitamin D therapy including native vitamin D supplements should be discontinued 7

Calcitriol represents an important therapeutic option for conditions requiring direct vitamin D hormone activity, particularly in patients with impaired ability to convert precursor forms to the active metabolite.