Usage
- Medical Conditions: Vitamin D3 (cholecalciferol) is primarily prescribed for preventing and treating vitamin D deficiency, which can manifest as rickets in children and osteomalacia in adults. It is also used to treat hypoparathyroidism and familial hypophosphatemia. It may be used in cases of osteoporosis, particularly when combined with calcium.
- Pharmacological Classification: Vitamin D3 is classified as a fat-soluble vitamin and hormone precursor.
- Mechanism of Action: Cholecalciferol is converted to calcifediol in the liver and then to calcitriol (the active form of vitamin D) in the kidneys. Calcitriol regulates calcium and phosphorus absorption from the intestines and promotes bone mineralization.
Alternate Names
- Vitamin D3
- Colecalciferol
- Activated 7-dehydrocholesterol
How It Works
- Pharmacodynamics: Vitamin D3 increases intestinal absorption of calcium and phosphorus. It mobilizes calcium from bone and decreases renal excretion of calcium and phosphorus, thereby maintaining serum calcium levels.
- Pharmacokinetics:
- Absorption: Cholecalciferol is readily absorbed from the gastrointestinal tract when taken with food containing fat.
- Metabolism: It is hydroxylated in the liver to 25-hydroxyvitamin D (calcidiol) and then in the kidneys to the active form, 1,25-dihydroxyvitamin D (calcitriol).
- Elimination: Calcitriol and its metabolites are primarily excreted in the bile and feces, with a small amount eliminated in urine.
- Mode of Action: Calcitriol binds to the vitamin D receptor (VDR), a nuclear receptor that regulates gene expression. It modulates the expression of proteins involved in calcium transport, bone mineralization, and cell differentiation.
- Elimination Pathways: Primarily biliary excretion. Minor renal excretion.
Dosage
Standard Dosage
Adults:
- Deficiency Treatment: 6,000 IU once daily for 3 months or a single dose of 300,000 IU, followed by a maintenance dose of 600 IU daily. Doses up to 10,000 IU daily may be used for severe deficiency.
- Maintenance: 600-800 IU daily.
Children:
- Deficiency Treatment: Variable depending on age and severity. See “Special Cases” and consult pediatric dosing guidelines.
- Maintenance: 400-600 IU daily for infants and 600-1,000 IU daily for children.
Special Cases:
- Elderly Patients: May require higher doses due to decreased skin synthesis and absorption.
- Patients with Renal Impairment: May require calcitriol (the active form) as the kidneys are responsible for converting vitamin D to its active form.
- Patients with Hepatic Dysfunction: Dosage adjustments may be necessary.
- Patients with Comorbid Conditions: Individualized dosing based on specific conditions.
Clinical Use Cases
- Dosage recommendations for specific medical settings like Intubation, Surgical Procedures, Mechanical Ventilation, Intensive Care Unit (ICU) Use, and Emergency Situations are not specifically tied to vitamin D3. These situations may reveal or exacerbate a pre-existing deficiency, requiring treatment.
Dosage Adjustments
- Dosage should be individualized based on serum 25-hydroxyvitamin D levels, patient response, and clinical condition.
Side Effects
Common Side Effects
- Hypercalcemia (high blood calcium levels) can lead to symptoms such as nausea, vomiting, constipation, weakness, and confusion.
- Hypercalciuria (high urine calcium levels) may increase the risk of kidney stones.
Rare but Serious Side Effects
- Severe hypercalcemia leading to renal failure and cardiac arrhythmias.
Long-Term Effects
- Long-term excessive intake can lead to nephrocalcinosis (calcium deposits in the kidneys).
Adverse Drug Reactions (ADR)
- Hypersensitivity reactions are rare.
Contraindications
- Hypercalcemia
- Vitamin D hypersensitivity
- Granulomatous diseases (e.g., sarcoidosis) as they may cause elevated levels of active vitamin D
Drug Interactions
- Thiazide diuretics: May increase the risk of hypercalcemia.
- Corticosteroids: May decrease the effectiveness of vitamin D.
- Anticonvulsants: May reduce vitamin D levels.
- Bile acid sequestrants (e.g., cholestyramine): May decrease vitamin D absorption.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: A (when used in recommended doses). High doses should be avoided during pregnancy.
- Breastfeeding: Vitamin D is excreted in breast milk. Supplementation in breastfeeding mothers may be necessary to maintain adequate vitamin D levels in both mother and infant.
Drug Profile Summary
- Mechanism of Action: Regulates calcium and phosphorus homeostasis, promotes intestinal absorption, and aids bone mineralization.
- Side Effects: Hypercalcemia, hypercalciuria, nausea, vomiting, constipation.
- Contraindications: Hypercalcemia, vitamin D hypersensitivity.
- Drug Interactions: Thiazide diuretics, corticosteroids, anticonvulsants.
- Pregnancy & Breastfeeding: Generally safe in recommended doses.
- Dosage: Varies depending on age, indication, and patient-specific factors. Monitor serum 25-hydroxyvitamin D levels.
- Monitoring Parameters: Serum calcium, phosphorus, 25-hydroxyvitamin D, and creatinine levels.
Popular Combinations
- Calcium: Often combined with vitamin D for enhanced bone health and treatment of osteoporosis.
Precautions
- General Precautions: Monitor serum calcium and phosphorus levels, particularly in patients with renal or hepatic impairment.
- Specific Populations: See above.
- Lifestyle Considerations: Adequate sun exposure can contribute to vitamin D synthesis.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Vit D3 Cholecalciferol?
A: The dosage depends on the patient’s age, health status, and the reason for taking the supplement. Typical doses range from 400-10,000 IU/day for adults.
Q2: Can I take more Vitamin D3 than recommended?
A: Exceeding recommended doses can lead to hypercalcemia. Follow medical advice for appropriate dosing.
Q3: What are the signs of vitamin D deficiency?
A: Symptoms can include fatigue, bone pain, muscle weakness, and increased risk of fractures.
Q4: Are there any food sources of vitamin D3?
A: Fatty fish (salmon, tuna), egg yolks, and fortified foods (milk, cereals) contain vitamin D3.
Q5: How does sunlight affect vitamin D levels?
A: Sunlight triggers vitamin D synthesis in the skin.
Q6: Can vitamin D3 interact with other medications?
A: Yes, potential interactions exist with some medications like thiazide diuretics, corticosteroids, and some anticonvulsants.
Q7: What is the difference between Vitamin D2 and D3?
A: Both increase serum vitamin D levels. D3 is considered more effective at raising and maintaining serum levels.
Q8: What is the role of Vitamin D3 in bone health?
A: Vitamin D3 promotes calcium absorption, which is essential for maintaining bone density and preventing osteoporosis.
Q9: How often should vitamin D levels be monitored?
A: This depends on individual factors and treatment goals. Monitoring is important for adjusting doses and avoiding toxicity.
