Vitamin D3 is an in vivo inactive molecule of vitamin D. To activate vitamin D3, it goes through two hydroxylation processes. The enzyme 25-hydroxylase (CYP27A1) and possibly other enzymes (such as CYP2R1) hydroxylate vitamin D3 in the liver to create the circulating prohormone 25-hydroxy vitamin D3 [25(OH)D3][1]. The kidneys use the enzyme 1-alpha-hydroxylase to carry out the second hydroxylation, resulting in 1,25-dihydroxycholecalciferol, or calcitriol, the biologically active form of vitamin D[1]. Vitamin D3 (2-10 μM; 24-48 hours) shows effects against proliferation that are dependent on both time and dose. After treating with 10 μM vitamin D3, the viability of 62% (IK), 52% (RL-95-2), and 55% (Hec-1A) is at its lowest point after 72 hours. However, there is no discernible decrease in viable cells after a 24-hour exposure[2]. Cholecalciferol (10 μM; 24-48 hours) exhibits notable increases in nuclear VDR staining and causes IK cells to become activated locally for VDR[1].

Cholecalciferol (oral gavage; 5 mg/kg; 7 days) increases the toxicity of CCl4 exclusively in the liver, as shown by elevated plasma levels of ALT and AST, two biochemical indicators of hepatic injury. Although renal calcium content does not significantly differ between mice, it significantly raises renal calcium levels in mice[3].

Male ddY mice on CCl4 toxicity[3]
5 mg/kg
Oral gavage; 5 mg/kg; 7 days

Absorption, Distribution and Excretion
Cholecalciferol is readily absorbed from the small intestine if fat absorption is normal. Moreover, bile is necessary for absorption as well. In particular, recent studies have determined aspects about the absorption of vitamin D, like the fact that a) the 25-hydroxyvitamin D metabolite of cholecalciferol is absorbed to a greater extent than the nonhydroxy form of cholecalciferol, b) the quantity of fat with which cholecalciferol is ingested does not appear to largely affect its bioavailability, and c) age does not apparently effect vitamin D cholecalciferol.
It has been observed that administered cholecalciferol and its metabolites are excreted primarily in the bile and feces.
Studies have determined that the mean central volume of distribution of administered cholecalciferol supplementation in a group of 49 kidney transplant patients was approximately 237 L.
Studies have determined that the mean clearance value of administered cholecalciferol supplementation in a group of 49 kidney transplant patients was approximately 2.5 L/day.
Readily absorbed from small intestine (proximal or distal); cholecalciferol may be absorbed more rapidly and completely than ergocalciferol.
Elimination: Biliary/renal. /Vitamin D and analogs/
Many vitamin D analogs are readily absorbed from the GI tract following oral administration if fat absorption is normal. The presence of bile is required for absorption of ergocalciferol and the extent of GI absorption may be decreased in patients with hepatic, biliary, or GI disease (e.g., Crohn's disease, Whipple's disease, sprue). Because vitamin D is fat soluble, it is incorporated into chylomicrons and absorbed via the lymphatic system; approximately 80% of ingested vitamin D appears to be absorbed systemically through this mechanism, principally in the small intestine. Although some evidence suggested that intestinal absorption of vitamin D may be decreased in geriatric adults, other evidence did not show clinically important age-related alterations in GI absorption of the vitamin in therapeutic doses. It currently is not known whether aging alters the GI absorption of physiologic amounts of vitamin D. /Vitamin D analogs/
After absorption, ergocalciferol and cholecalciferol enter the blood via chylomicrons of lymph and then associate mainly with a specific alpha-globulin (vitamin D-binding protein). The hydroxylated metabolites of ergocalciferol and cholecalciferol also circulate associated with the same alpha-globulin. 25-Hydroxylated ergocalciferol and cholecalciferol are stored in fat and muscles for prolonged periods. Once vitamin D enters systemic circulation from lymph via the thoracic duct or from skin, it accumulates in the liver within a few hours.
For more Absorption, Distribution and Excretion (Complete) data for CHOLECALCIFEROL (7 total), please visit the HSDB record page.

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Metabolism / Metabolites
Within the liver, cholecalciferol is hydroxylated to calcifediol (25-hydroxycholecalciferol) by the enzyme vitamin D-25-hydroxylase. At the kidney, calcifediol subsequently serves as a substrate for 1-alpha-hydroxylase, yielding calcitriol (1,25-dihydroxycholecalciferol), the biologically active form of vitamin D3.
Metabolic activation of cholecalciferol and ergocalciferol occurs in 2 steps, the first in the liver and the second in the kidneys. Metabolic activation of calcifediol occurs in the kidneys; dihydrotachysterol, alfacalcidol and doxercalciferol are activated in the liver.
Normal combined (ie, 25-hydroxyvitamin D) plasma concentrations of 25-hydroxycholecalciferol (calcifediol) and 25-hydroxyergocalciferol, which are the major circulating metabolites of cholecalciferol and ergocalciferol, have been reported to range from 8-80 ng/mL, depending on the assay used, and vary with exposure to UV light. A commonly reported range for the lower limit of normal is 8-15 ng/mL, depending on geographic location (eg, Southern California would be higher than Massachusetts).
In the liver, ergocalciferol and cholecalciferol are converted in the mitochondria to their 25-hydroxy derivatives by the enzyme vitamin D 25-hydroxylase. Vitamin D 25-hydroxylase activity is regulated in the liver by concentrations of vitamin D and its metabolites; therefore, increases in the systemic circulation of the 25-hydroxy metabolites following exposure to sunlight or ingestion of vitamin D are relatively modest compared with cumulative production or intake of the vitamin. Serum concentrations of nonhydroxylated vitamin D are short-lived as a result of storage in fat or metabolism in the liver. In the kidneys, these metabolites are further hydroxylated at the 1 position by the enzyme vitamin D 1-hydroxylase to their active forms, 1,25-dihydroxycholecalciferol (calcitriol) and 1,25-dihydroxyergocalciferol. ... Activity of the vitamin D 1-hydroxylase enzyme requires molecular oxygen, magnesium ion, and malate and is regulated principally by PTH in response to serum concentrations of calcium and phosphate, and perhaps by circulating concentrations of 1,25-dihydroxyergocalciferol and 1,25-dihydroxycholecalciferol. Other hormones (ie, cortisol, estrogens, prolactin, and growth hormone) also may influence the metabolism of cholecalciferol and ergocalciferol.
The hepatic enzyme system responsible for 25-hydroxylation of vitamin D /(vitamin D-25 hydroxylase)/ is associated with the microsomal and mitochondrial fractions of homogenates and requires NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) and molecular oxygen. ... The enzyme system /in kidney/ responsible for 1-hydroxylation of 25-OHD (25-hydroxycholecalciferol) /(25-OHD-1-alpha-hydroxylase)/ is associated with mitochondria in the proximal tubules. It is a mixed function oxidase and requires molecular oxygen and NADPH as cofactors. Cytochrome P450, a flavoprotein, and ferredoxin are components of the enzyme complex.
Within the liver, cholecalciferal is hydroxylated to calcidiol (25-hydroxycholecalciferol) by the enzyme 25-hydroxylase. Within the kidney, calcidiol serves as a substrate for 1-alpha-hydroxylase, yielding calcitriol (1,25-dihydroxycholecalciferol), the biologically active form of vitamin D3.
Half Life: Several weeks

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Biological Half-Life
At this time, there have been resources that document the half-life of cholecalciferol as being about 50 days while other sources have noted that the half-life of calcitriol (1,25-dihydroxyvitamin D3) is approximately 15 hours while that of calcidiol (25-hydroxyvitamin D3) is about 15 days. Moreover, it appears that the half-lives of any particular administration of vitamin d can vary due to variations in vitamin d binding protein concentrations and genotype in particular individuals.
The Vitamin /D/ disappears from plasma with a half-life of 19 to 25 hr but is stored in fat depots for prolonged periods. ... The 25-hydroxy derivative has a biological half-life of 19 days ... The plasma half-life of calcitriol /(1,25-dihydroxy-vitamin D)/ is estimated to be between 3 and 5 days in human beings ...

Toxicity Summary
The first step involved in the activation of vitamin D3 is a 25-hydroxylation which is catalysed by the 25-hydroxylase in the liver and then by other enzymes. The mitochondrial sterol 27-hydroxylase catalyses the first reaction in the oxidation of the side chain of sterol intermediates. The active form of vitamin D3 (calcitriol) binds to intracellular receptors that then function as transcription factors to modulate gene expression. Like the receptors for other steroid hormones and thyroid hormones, the vitamin D receptor has hormone-binding and DNA-binding domains. The vitamin D receptor forms a complex with another intracellular receptor, the retinoid-X receptor, and that heterodimer is what binds to DNA. In most cases studied, the effect is to activate transcription, but situations are also known in which vitamin D suppresses transcription. Calcitriol increases the serum calcium concentrations by: increasing GI absorption of phosphorus and calcium, increasing osteoclastic resorption, and increasing distal renal tubular reabsorption of calcium. Calcitriol appears to promote intestinal absorption of calcium through binding to the vitamin D receptor in the mucosal cytoplasm of the intestine. Subsequently, calcium is absorbed through formation of a calcium-binding protein.

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Protein Binding
The protein binding documented for cholecalciferol is 50 to 80%. Specifically, in the plasma, vitamin D3 (from either diet or the skin) is bound to vitamin D-binding protein (DBP) produced in the liver, for transport to the liver. Ultimately, the form of vitamin D3 reaching the liver is 25-hydroxylated, and such 25-hydroxycholecalciferol is bound to DBP (α2-globulin) whilst circulating in the plasma.

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Toxicity Data
LC50 (rat) = 130-380 ppm/4hr

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Interactions
Corticosteroids counteract the effects of vitamin D analogs. /Vitamin D analogs/
Concurrent administration of thiazide diuretics and pharmacologic doses of vitamin D analogs in patients with hypoparathyroidism may result in hypercalcemia which may be transient and self-limited or may require discontinuance of vitamin D analogs. Thiazide-induced hypercalcemia in hypoparathyroid patients is probably caused by increased release of calcium from bone. /Vitamin D analogs/
Excessive use of mineral oil may interfere with intestinal absorption of vitamin D analogs. /Vitamin D analogs/
Orlistat may result in decreased GI absorption of fat-soluble vitamins such as vitamin D analogs. At least 2 hours should elapse between (before or after) any orlistat dose and vitamin D analog administration ... . /Vitamin D analogs/
For more Interactions (Complete) data for CHOLECALCIFEROL (6 total), please visit the HSDB record page.

[1]. Nazik Al-Hashimi, et al. Cholecalciferol.

[2]. Role of local bioactivation of vitamin D by CYP27A1 and CYP2R1 in the control of cell growth in normal endometrium and endometrial carcinoma. Lab Invest. 2014 Jun;94(6):608-22.

[3]. Vitamin D3-induced hypercalcemia increases carbon tetrachloride-induced hepatotoxicity through elevated oxidative stress in mice. PLoS One. 2017 Apr 27;12(4):e0176524.

Therapeutic Uses
Bone Density Conservation Agents; Vitamins
MEDICATION (VET): Nutritional factor (Antirachitic)
Therapeutic doses of specific vitamin D analogs are used in the treatment of chronic hypocalcemia, hypophosphatemia, rickets, and osteodystrophy associated with various medical conditions including chronic renal failure, familial hypophosphatemia, and hypoparathyroidism (postsurgical or idiopathic, or pseudohypoparathyroidism). Some analogs have been found to reduct elevated parathyroid hormone concentrations in patients with renal osteodystrophy associated with hyperparathyroidism. Theoretically, any of the vitamin D analogs may be used for the above conditions, However, because of their pharmacologic properties, some may be more useful in certain situations than others. Alfacalcidol, calcitriol, and dihydrotachysterol are usually preferred in patients with renal failure since these patients have impaired ability to synthesize calcitriol from cholecalciferol and ergocalciferol; therefore, the response is more predictable. In addition, their shorter half-lives may make toxicity easier to manage (hypercalcemia reverses more quickly). Ergocalciferol may not be the preferred agent in the treatment of familial hypophosphatemia or hypoparathyroidism because the large doses needed are associated with a risk of overdose and hypercalcemia; dihydrotachysterol and calcitriol may be preferred. /Included in US product labeling/

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Drug Warnings
Studies have shown that the elderly may have an increased need for vitamin D due to a possible decrease in the capacity of the skin to produce previtamin D3 or a decrease in exposure to the sun or impaired renal function or impaired vitamin D absorption.
Doses of vitamin D analogs that do not exceed the physiologic requirement are usually nontoxic. However, some infants and patients with sarcoidosis or hypoparathyroidism may have increased sensitivity to vitamin D analogs. /Vitamin D analogs/
Acute or chronic administration of excessive doses of vitamin D analogs or enhanced responsiveness to physiologic amounts of ergocalciferol or cholecalciferol may lead to hypervitaminosis D manifested by hypercalcemia. /Vitamin D analogs/
Decreased renal function without hypercalcemia has also been reported in patients with hypoparathyroidism after long-term vitamin D analog therapy. Before therapy with vitamin D analogs is initiated, serum phosphate concentrations must be controlled. To avoid ectopic calcification, the serum calcium (in mg/dL) times phosphorus (in mg/dL) should not be allowed to exceed 70. Because administration of vitamin D analogs may increase phosphate absorption, patients with renal failure may require adjustment in the dosage of aluminum-containing antacids used to decrease phosphate absorption. /Vitamin D analogs/
For more Drug Warnings (Complete) data for CHOLECALCIFEROL (10 total), please visit the HSDB record page.

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Pharmacodynamics
The in vivo synthesis of the predominant two biologically active metabolites of vitamin D occurs in two steps. The first hydroxylation of vitamin D3 cholecalciferol (or D2) occurs in the liver to yield 25-hydroxyvitamin D while the second hydroxylation happens in the kidneys to give 1, 25-dihydroxyvitamin D. These vitamin D metabolites subsequently facilitate the active absorption of calcium and phosphorus in the small intestine, serving to increase serum calcium and phosphate levels sufficiently to allow bone mineralization. Conversely, these vitamin D metabolites also assist in mobilizing calcium and phosphate from bone and likely increase the reabsorption of calcium and perhaps also of phosphate via the renal tubules. There exists a period of 10 to 24 hours between the administration of cholecalciferol and the initiation of its action in the body due to the necessity of synthesis of the active vitamin D metabolites in the liver and kidneys. It is parathyroid hormone that is responsible for the regulation of such metabolism at the level of the kidneys.

C27H44O

384.6377

384.339

C, 84.31; H, 11.53; O, 4.16

67-97-0

Vitamin D3-d7;1627523-19-6;3-epi-Vitamin D3;57651-82-8;Vitamin D3-13C3;Vitamin D3-d3;80666-48-4;Vitamin D3-13C5

5280795

White to off-white solid powder

1.0±0.1 g/cm3

496.4±24.0 °C at 760 mmHg

83-86 °C(lit.)

214.2±15.1 °C

0.0±2.9 mmHg at 25°C

1.523

9.72

1

1

6

28

610

5

O([H])[C@@]1([H])C([H])([H])C([H])([H])C(=C([H])[H])/C(/C1([H])[H])=C(/[H])\C(\[H])=C1/C([H])([H])C([H])([H])C([H])([H])[C@@]2(C([H])([H])[H])[C@@]/1([H])C([H])([H])C([H])([H])[C@]2([H])[C@]([H])(C([H])([H])[H])C([H])([H])C([H])([H])C([H])([H])C([H])(C([H])([H])[H])C([H])([H])[H]

QYSXJUFSXHHAJI-YRZJJWOYSA-N

InChI=1S/C27H44O/c1-19(2)8-6-9-21(4)25-15-16-26-22(10-7-17-27(25,26)5)12-13-23-18-24(28)14-11-20(23)3/h12-13,19,21,24-26,28H,3,6-11,14-18H2,1-2,4-5H3/b22-12+,23-13-/t21-,24+,25-,26+,27-/m1/s1

(1S,3Z)-3-[(2E)-2-[(1R,3aS,7aR)-7a-methyl-1-[(2R)-6-methylheptan-2-yl]-2,3,3a,5,6,7-hexahydro-1H-inden-4-ylidene]ethylidene]-4-methylidenecyclohexan-1-ol

Activated 7-dehydrocholesterol; Cholecalciferol; Calciol; Vitamin D3; Colecalciferol; Arachitol; Ricketon; Trivitan; Vigorsan; Deparal; Vigantol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: (1). This product requires protection from light (avoid light exposure) during transportation and storage.  (2). Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture.  (3). This product is not stable in solution, please use freshly prepared working solution for optimal results.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~259.98 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (5.41 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: 2.08 mg/mL (5.41 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (5.41 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)