Drug compounds have included stable heavy isotopes of carbon, hydrogen, and other elements, mostly as quantitative tracers while the drugs were being developed. Because deuteration may have an effect on a drug's pharmacokinetics and metabolic properties, it is a cause for concern [1].

Absorption, Distribution and Excretion
Cholecalciferol is readily absorbed from the small intestine if fat absorption is normal. Furthermore, bile is also essential for absorption. In particular, recent studies have identified several aspects of vitamin D absorption, such as: a) the 25-hydroxyvitamin D metabolite of cholecalciferol is absorbed more readily than the non-hydroxy form of cholecalciferol; b) the amount of fat ingested with cholecalciferol appears to have little effect on its bioavailability; and c) age does not appear to affect the absorption of vitamin D by cholecalciferol. Observations have shown that ingested cholecalciferol and its metabolites are primarily excreted via bile and feces. Studies have shown that in 49 kidney transplant patients, the mean central volume of distribution after cholecalciferol supplementation was approximately 237 liters. Studies have also shown that in 49 kidney transplant patients, the mean clearance after cholecalciferol supplementation was approximately 2.5 liters/day. It is readily absorbed from the small intestine (proximal or distal); the rate and completeness of cholecalciferol absorption may be superior to ergocalciferol.
Excretion route: Bile/Kidney. /Vitamin D and its analogues/
Many vitamin D analogues are rapidly absorbed by the gastrointestinal tract after oral administration if fat absorption is normal. Ergocalciferol absorption requires the presence of bile, and patients with liver, biliary tract, or gastrointestinal diseases (e.g., Crohn's disease, Whipple's disease, celiac disease) may experience reduced gastrointestinal absorption. 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, primarily in the small intestine. While some evidence suggests that intestinal absorption of vitamin D may be reduced in older adults, other evidence does not show clinically significant age-related changes in gastrointestinal absorption of vitamin D at therapeutic doses. It is currently unclear whether aging alters the gastrointestinal absorption of physiological doses of vitamin D. /Vitamin D analogues/
After absorption, ergocalciferol and cholecalciferol enter the bloodstream via lymphatic chylomicrons and then bind primarily to a specific α-globulin (vitamin D-binding protein). The hydroxylated metabolites of ergocalciferol and cholecalciferol also cycle with the same α-globulin. 25-hydroxylated ergocalciferol and cholecalciferol can be stored for extended periods in fat and muscle. Vitamin D enters the systemic circulation via the thoracic duct from the lymphatic system or skin and accumulates in the liver within hours. For more complete data on the absorption, distribution, and excretion of cholecalciferol (a total of 7 types), please visit the HSDB record page. Metabolites/Metabolites In the liver, cholecalciferol is hydroxylated to calcidiol (25-hydroxycholecalciferol) by vitamin D-25-hydroxylase. In the kidneys, calcidiol then acts as a substrate for 1-α-hydroxylase to generate calcitriol (1,25-dihydroxycholecalciferol), the biologically active form of vitamin D3. The metabolic activation of cholecalciferol and ergocalciferol occurs in two steps, first in the liver and second in the kidneys. The metabolic activation of calcidiol occurs in the kidneys; dihydrotachysterol, alfacalcidol, and docecalcidol are activated in the liver. The normal plasma total concentration (i.e., 25-hydroxyvitamin D) of the main circulating metabolites of cholecalciferol and ergocalciferol—25-hydroxycholecalciferol (calcidiol) and 25-hydroxyergocalciferol—has been reported to range from 8 to 80 ng/mL, depending on the assay method used and varying with ultraviolet radiation. Depending on geographical location (e.g., values in Southern California are higher than in Massachusetts), the lower limit of normal is typically reported to be 8–15 ng/mL. In the liver, ergocalciferol and cholecalciferol are converted to their 25-hydroxy derivatives in the mitochondria by vitamin D 25-hydroxylase. The activity of vitamin D 25-hydroxylase in the liver is regulated by the concentrations of vitamin D and its metabolites; therefore, the increase in systemic 25-hydroxyl metabolites after sunlight exposure or vitamin D ingestion is relatively small compared to the cumulative production or intake of vitamin D. Due to storage in adipose tissue or metabolism in the liver, the concentration of unhydroxylated vitamin D in serum is short-lived. In the kidneys, these metabolites are further hydroxylated at the 1-position by vitamin D 1-hydroxylase to produce their active forms: 1,25-dihydroxycholecalciferol (calcitriol) and 1,25-dihydroxyergocalciferol. The activity of vitamin D 1-hydroxylase requires molecular oxygen, magnesium ions, and malate, and is primarily regulated by parathyroid hormone (PTH), which is influenced by serum calcium and phosphate concentrations, and possibly also by circulating concentrations of 1,25-dihydroxyergocalciferol and 1,25-dihydroxycholecalciferol. Other hormones (such as cortisol, estrogen, prolactin, and growth hormone) may also affect the metabolism of cholecalciferol and ergocalciferol. The liver enzyme system responsible for vitamin D 25-hydroxylation (vitamin D-25-hydroxylase) is associated with the microsomal and mitochondrial components of the homogenate and requires NADPH (reduced nicotinamide adenine dinucleotide phosphate) and molecular oxygen. The kidney enzyme system responsible for 1-hydroxylation of 25-hydroxyvitamin D (25-OHD) (25-OHD-1-α-hydroxylase) is associated with the mitochondria of the proximal tubules. It is a mixed-function oxidase that requires molecular oxygen and NADPH as cofactors. Cytochrome P450 (a flavoprotein) and ferroredoxin are components of this enzyme complex.
Biological Half-Life
Currently, some data indicate that the half-life of cholecalciferol is approximately 50 days, while others suggest that the half-life of calcitriol (1,25-dihydroxyvitamin D3) is approximately 15 hours, and that of calcidiol (25-hydroxyvitamin D3) is also approximately 15 days. Furthermore, the half-life of vitamin D appears to vary between individuals due to differences in vitamin D-binding protein concentration and genotype. The half-life of vitamin D in plasma is 19 to 25 hours, but it is stored for a long time in adipose tissue. …The biological half-life of 25-hydroxyvitamin D derivatives is 19 days… It is estimated that the plasma half-life of calcitriol (1,25-dihydroxyvitamin D) in the human body is 3 to 5 days…

Protein Binding
Recorded protein binding rates for cholecalciferol range from 50% to 80%. Specifically, in plasma, vitamin D3 (from diet or skin) binds to vitamin D-binding protein (DBP) produced by the liver for transport to the liver. Ultimately, vitamin D3 reaching the liver is 25-hydroxylated, and this 25-hydroxycholecalciferol binds to DBP (α2-globulin) during plasma circulation. Toxicity Data LC50 (rat) = 130-380 ppm/4 hours Interactions Corticosteroids can antagonize the effects of vitamin D analogs. /Vitamin D Analogs/ In patients with hypoparathyroidism, concomitant use of thiazide diuretics and pharmacological doses of vitamin D analogs may lead to hypercalcemia, which may be transient and self-limiting, or may require discontinuation of vitamin D analogs. Hypercalcemia induced by thiazide diuretics in patients with hypoparathyroidism may be due to increased calcium release from bones. /Vitamin D analogs/
Excessive use of mineral oil may interfere with intestinal absorption of vitamin D analogs. /Vitamin D analogs/
Orlistat may reduce the gastrointestinal absorption of fat-soluble vitamins (such as vitamin D analogs). At least 2 hours should be allowed between taking any dose of orlistat and taking a vitamin D analog (before or after). /Vitamin D analogs/
For more complete data on interactions with cholecalciferol (6 in total), please visit the HSDB records page.

[1]. Impact of Deuterium Substitution on the Pharmacokinetics of Pharmaceuticals. Ann Pharmacother. 2019 Feb;53(2):211-216.

[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.

Therapeutic Uses
Bone mineralization protectants; Vitamins
Veterinary drugs: Nutritional factors (anti-rickets drugs)
Therapeutic doses of specific vitamin D analogs are used to treat chronic hypocalcemia, hypophosphatemia, rickets, and osteodystrophy associated with a variety of diseases, including chronic renal failure, familial hypophosphatemia, and hypoparathyroidism (postoperative, idiopathic, or pseudohypoparathyroidism). Some analogs have been found to reduce elevated parathyroid hormone levels in patients with renal osteodystrophy accompanied by hyperparathyroidism. Theoretically, any vitamin D analog can be used to treat the above-mentioned diseases, but due to differences in their pharmacological properties, some analogs may be more effective than others in specific situations. For patients with renal failure, alfacalcidol, calcitriol, and dihydrotachysterol are usually preferred because these patients have impaired ability to synthesize calcitriol, thus making the efficacy more predictable. Furthermore, these drugs have shorter half-lives, making toxicity easier to control (hypercalcemia reverses more quickly). Ergocalciferol may not be the first-line treatment for familial hypophosphatemia or hypoparathyroidism because the required high doses carry the risk of overdose and hypercalcemia; dihydrotachysterol and calcitriol may be more suitable in these cases. /US product label contains/

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Drug Warnings
Studies have shown that older adults may have increased vitamin D requirements due to decreased skin production of vitamin D3 precursors, reduced sun exposure, impaired kidney function, or impaired vitamin D absorption.
Vitamin D analogs at doses not exceeding physiological requirements are generally non-toxic. However, some infants and patients with sarcoidosis or hypoparathyroidism may be more sensitive to vitamin D analogs. /Vitamin D Analogs/
Acute or chronic overdose of vitamin D analogs, or an enhanced response to physiological doses of ergocalciferol or cholecalciferol, can lead to vitamin D overdose, manifested as hypercalcemia. /Vitamin D Analogs/
It has been reported that patients with hypoparathyroidism who have been treated with vitamin D analogs for a long time have also experienced a decline in renal function, but without hypercalcemia. Serum phosphate concentrations must be controlled before starting vitamin D analog treatment. To avoid ectopic calcification, the ratio of serum calcium (mg/dL) to phosphorus (mg/dL) should not exceed 70. Because taking vitamin D analogs may increase phosphate absorption, patients with renal failure may need to adjust the dosage of aluminum-containing antacids used to reduce phosphate absorption. /Vitamin D Analogs/
For more complete data on drug warnings for cholecalciferol (10 in total), please visit the HSDB record page.

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Pharmacodynamics
The synthesis of the two main bioactive metabolites of vitamin D in vivo occurs in two steps. The first hydroxylation of vitamin D3 (cholecalciferol) (or vitamin D2) occurs in the liver, producing 25-hydroxyvitamin D; the second hydroxylation occurs in the kidneys, producing 1,25-dihydroxyvitamin D. These vitamin D metabolites then promote the absorption of calcium and phosphorus in the small intestine, thereby increasing serum calcium and phosphorus levels to promote bone mineralization. Conversely, these vitamin D metabolites also help mobilize calcium and phosphorus from bones and may increase the reabsorption of calcium (and perhaps phosphorus) through the renal tubules. Because the liver and kidneys need to synthesize active vitamin D metabolites, it takes 10 to 24 hours from the time cholecalciferol is taken to its effect in the body. Parathyroid hormone is responsible for regulating this metabolism at renal levels.

C27H44O

387.656153678894

387.358

80666-48-4

Vitamin D3;67-97-0

117064495

White to off-white solid powder

7.619

1

1

6

28

610

5

[2H]C(=C\1CC[C@@H](C/C1=C(\[2H])/C=C/2\CCC[C@]3([C@H]2CC[C@@H]3[C@H](C)CCCC(C)C)C)O)[2H]

QYSXJUFSXHHAJI-GLSUUORTSA-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/i3D2,13D

(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]-1-deuterioethylidene]-4-(dideuteriomethylidene)cyclohexan-1-ol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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