There are so many vitamin D drugs. What’s the difference and how to use them correctly?

What are the differences between vitamin D and its analogues and the precautions for use?
Vitamin D can act on the vitamin D receptor (VDR) of bone, intestine, kidney, parathyroid gland and other cells, regulate calcium balance and bone metabolism, coordinate neuromuscular function, regulate immune function and cell proliferation and differentiation.
It can be used for hypocalcemia, vitamin D-dependent rickets, osteoporosis, secondary hyperparathyroidism (SHPT), prevention and treatment of autoimmune disease, cardiovascular disease and tumor and other chronic diseases.
01
Differences between vitamin D and its analogues
Common vitamin D includes Vitamin D2 and vitamin D3; Activated vitamin D mainly includes 25 (OH) D3 (ossifying diol), 1 α-( Oh) D2 (doxycalciferol), 1 α-( Among them, active vitamin D includes calcitriol, paricalcitriol and Masha calcitriol. Active vitamin D is also known as vdra (vitamin D receptor agonist), According to the different affinity of VDR to different organs, it can be divided into selective vdra (paricalcitol, Masha calcitol) and non selective vdra (calcitriol).
Table 1: differences between vitamin D and its analogues
classification
medicine
compare
Common vitamin D
Vitamin D2, vitamin D3
① Vitamin D is metabolized and activated to 1,25 (OH) 2D3 by liver and kidney.
② There was no significant difference in VDR affinity between intestinal mucosa cells and parathyroid cells.
③ Vitamin D2 has a relatively low affinity for vitamin D binding protein (VDBP) and a short half-life, which is more resistant to drug overdose than vitamin D3. Compared with vitamin D2, vitamin D3 has the advantages of slow tissue clearance and high bioavailability.
Activate vitamin D
Ossifying diol, docetaxel, alfacalcidol, calcitriol, paricalcitol, Masha calcitol, etc
① Ossifying diol does not require liver metabolic activation, but requires kidney 1 α Hydroxylase has biological activity only after it is activated. Doxycalciferol and alfacalcidol do not need the activation of kidney metabolism, but need the activation of liver 25 hydroxylase to have biological activity. Active vitamin D (calcitriol, paricalcitol and Masha calcitol) has complete biological activity.
② There was no significant difference in the VDR affinity of intestinal mucosa cells and parathyroid cells among calcitriol, doxycalciferol, alfacalcidol and calcitriol. The affinity of paricalcitol and mashacalcidol for VDR of parathyroid cells was stronger than that of intestinal mucosal cells, the intestinal calcium transport was relatively low, and the incidence of hypercalcemia was low.
③ The half-life of alfacalcidol was longer than that of calcitriol. It took about one week for alfacalcidol to disappear. The half-life of calcitriol was short and the effect disappeared quickly (2-3 days).
④ Paricalcitol can also up regulate the expression of calcium sensitive receptor (CaSR) in parathyroid, enhance the sensitivity of parathyroid cells to calcium, and inhibit the secretion of parathyroid hormone more than calcitriol.
⑤ The risk of high urinary calcium caused by activated vitamin D was significantly higher than that caused by common vitamin D, especially when combined with calcium supplement. The higher the dose of activated vitamin D, the higher the risk of hypercalcemia.
02
Precautions for the use of vitamin D and its analogues
Adverse reactions of vitamin D and its analogues included constipation, diarrhea, persistent headache, myalgia, bone pain, hypertension, vitamin D poisoning, hypercalcemia, hypercalciuria, soft tissue calcification, kidney stones, pruritus, arrhythmia, mental disorders, nocturnal polyuria, etc.
Table 2: precautions for the use of vitamin D and its analogues
Vitamin D and its analogues
matters needing attention
Drug interactions
① The common adverse reactions were nausea, vomiting, loss of appetite, constipation, diarrhea, persistent headache, thirst, metallic taste in the mouth, fatigue and weakness. Some of them may have bone pain, turbid urine, convulsion, hypertension, increased sensitivity of eyes to light stimulation, arrhythmia, occasional myalgia, mental abnormality, pruritus, nocturnal polyuria, severe abdominal pain (sometimes misdiagnosed as pancreatitis), and so on Weight loss.
② Hypercalcemia: seen in excessive intake of vitamin D, manifested as nausea, vomiting, constipation, vertigo, myasthenia, bone pain, etc. One patient had granulomatous diseases such as pulmonary tuberculosis and active sarcoidosis α‑ The increase of hydroxylase activity increases the risk of hypercalcemia. Hypercalcemia is forbidden.
③ Hypercalciuria and kidney stones: vitamin D can increase urinary calcium excretion and cause hypercalciuria. Combination with calcium increases the risk of kidney stones. Renal calculi should be used with caution.
④ Soft tissue calcification: vitamin D can increase the body’s calcium absorption. Excessive calcium load may cause vascular calcification, calcium deposition in soft tissues such as kidneys and joints, and lead to increased blood pressure, increased cardiovascular events, renal failure and growth arrest of children.
⑤ Vitamin D poisoning: improper large dose treatment or accidental overdose can cause vitamin D poisoning, which is rare. When serum 25 (OH) d > 500 nmol / L continuously, it can be considered as potential vitamin D poisoning. Common nonspecific symptoms include nausea, vomiting, anorexia, loss of appetite, weight loss, polyuria, arrhythmia, etc. obvious symptoms include vascular and tissue calcification caused by chronic continuous increase of blood calcium level, affecting the heart, blood vessels and kidneys.
⑥ Excessive inhibition of PTH secretion by active vitamin D may aggravate bone loss and lead to low transport osteopathy.
⑦ Vitamin D treatment can reduce the concentration of serum phosphatase, increase the concentration of serum calcium, cholesterol, phosphate and magnesium and the concentration of urine calcium and phosphate. Patients with arteriosclerosis, cardiac insufficiency, hypercholesterolemia, hyperphosphatemia and high sensitivity to vitamin D should be cautious.
⑧ During the treatment, pay attention to monitor blood calcium and urine calcium, especially those who supplement calcium at the same time.
① Combined with digitalis, if vitamin D causes hypercalcemia, it is easy to induce arrhythmia.
② Barbital, phenytoin sodium, anticonvulsant drugs and promethasone can reduce the effect of vitamin D, and vitamin D3 should be supplemented for long-term use.
③ Vitamin D combined with magnesium containing drugs can cause hypermagnesemia, especially in patients with chronic renal failure.
④ When combined with calcium, the risk of hypercalcemia or hypercalcemia is increased.
⑤ It can counteract the effect of calcitonin on hypercalcemia.
⑥ Combined with thiazide diuretics can increase the risk of hypercalcemia.
⑦ The combination of calcium, phosphorus and vitamin D can induce hyperphosphatemia.

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