Difference between Vitamin D, calcitriol, and Alfacalciol
Commonly used vitamin D and its analogues are: vitamin D2, vitamin D3, calcifediol, calcitriol, alfacalcidol, paricalcitol, and calcipotriol. What are the differences between these seven vitamin D-like drugs?
I. Differences between Vitamin D3 and Vitamin D2
Vitamin D2 and D3 are collectively referred to as vitamin D. Vitamin D2 is the product of UV radiation from plants or fungi. Vitamin D3 is the product of UV radiation from human skin. – In addition to wild fatty fish, foods contain only trace amounts of vitamin D and cannot be supplemented with vitamin D.
In the regulation of human bone calcium metabolism, vitamin D3 activity is 2 to 4 times that of vitamin D2. Vitamin D3 is recommended as a vitamin D supplement. – Infants and young children can use vitamin D drops (vitamin D3 400IU / tablets), careful selection of cod liver oil (containing vitamins A and D).
Nutritional intake of vitamin D recommendations (for clinical reference only)
II. Seven Analogs, Differences in Metabolism in the Body
Vitamin D2, D3, calcifediol, and alfacalcidol cannot bind directly to the vitamin D receptor and is inactive. Calcitriol, paricalcitol, and calcipotriol can bind directly to vitamin D receptors and have their own activity.
III. Seven Analogues, Differences in Indications
Special reminder: long-term excessive oral vitamin D can cause hypercalcemia. A moderate degree of hypercalcemia will completely inhibit children’s growth and development for more than 6 months, and the effect on height cannot be completely corrected. – The risk of hypercalcemia caused by calcitriol is greater than that of vitamin D.
1. Prevent nutritional rickets
For the prevention of nutritional rickets, oral vitamin D (400 U ~ 800 U/day) – rickets treatment is the first choice, oral vitamin D (1000 U/day), or calcidiol (50 ~ 100 μg/day).
2. Prevention and treatment of osteoporosis
Prevention of osteoporosis: vitamin D (600 ~ 1000 U / day); treatment of osteoporosis: vitamin D or calcifediol can be used. – Patients older than 65 years or who have reduced renal function: oral calcitriol (0.25 to 0.5 μg/day) or oral alfacalcidol (0.25 to 1.0 μg)/day is recommended.
3. Treatment of metabolic rickets and osteomalacia
In patients with chronic kidney disease, 1α-hydroxylase activity is decreased, and the synthesis of calcitriol in the kidneys is reduced, which can cause osteomalacia and renal osteodystrophy.—Alkaline triol is preferred: Half-life 4 to 6 hours, 0.25~ each time 0.5 μg, 1 or 2 times daily, or Alfacalcidol: half-life of 17.6 hours, 0.5 μg each time, once daily.
4. Treatment of hypoparathyroidism
Calcitriol is preferred and the starting dose is 0.25 μg per day in the morning.
5. Secondary hyperparathyroidism in patients with chronic renal failure receiving hemodialysis
Paricalcitol, which binds to vitamin D receptors, inhibits the synthesis and secretion of parathyroid hormone and has little effect on blood calcium and serum phosphorus. 0.04 to 0.1 μg, single injection, administered at any time during dialysis.
6. Treatment of psoriasis
Calcipotriol, topical application can directly bind to vitamin D receptors in skin cells and inhibit the proliferation of psoriasis lesions. Calcipotriol is used externally and about 1% to 5% can be absorbed through the skin. If you exceed the recommended amount, you may cause elevated serum calcium.
