1. Clinical Overview
Vitamin D3 (Cholecalciferol) 60,000 IU is a high-dose, orally administered, fat-soluble vitamin supplement used primarily for the rapid correction of severe vitamin D deficiency. It is a prohormone that undergoes two hydroxylations in the body to become the active hormone calcitriol (1,25-dihydroxycholecalciferol). In the Indian context, it is a cornerstone therapy due to the high prevalence of deficiency linked to dietary habits, skin pigmentation, and limited sun exposure.
| Onset | Duration | Bioavailability |
|---|---|---|
| Serum 25(OH)D levels begin to rise within 24-48 hours of oral administration. | The half-life of 25(OH)D is approximately 15-30 days. A single 60,000 IU dose can maintain elevated serum levels for several weeks, supporting weekly or monthly dosing regimens. | Approximately 55-99% when taken with a fatty meal. Absorption is highly dependent on dietary fat. |
2. Mechanism of Action
Vitamin D3 is a prohormone. It is converted to 25(OH)D in the liver and then to the active form, 1,25(OH)2D (calcitriol), in the kidneys. Calcitriol binds to the Vitamin D Receptor (VDR), a nuclear receptor. The VDR-ligand complex heterodimerizes with the Retinoid X Receptor (RXR) and binds to Vitamin D Response Elements (VDREs) in the promoter regions of target genes, regulating their transcription.
3. Indications & Uses
- Treatment of severe Vitamin D deficiency (Serum 25(OH)D < 20 ng/mL)
- Prevention and treatment of nutritional rickets and osteomalacia
- Supplementation in osteoporosis (as part of combination therapy with calcium and bisphosphonates)
- Hypoparathyroidism (as part of management with calcium)
4. Dosage & Administration
Adult Dosage: For Deficiency Correction: 60,000 IU once weekly for 8-12 weeks, followed by a maintenance dose of 60,000 IU once monthly or 1000-2000 IU daily. For Osteoporosis: 60,000 IU once monthly, often co-prescribed with calcium and an anti-resorptive agent.
Administration: Take orally with the largest meal of the day, preferably one containing dietary fat (e.g., milk, curd, nuts, oil) to enhance absorption. Capsule/softgel can be swallowed whole. Do not crush or chew. Maintain adequate dietary calcium intake (approx. 1000-1200 mg/day).
5. Side Effects
Common side effects may include:
- Nausea
- Constipation
- Dry mouth
- Metallic taste
- Headache
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Thiazide Diuretics (e.g., Hydrochlorothiazide) | Increased risk of hypercalcemia due to reduced renal calcium excretion. | Major |
| Orlistat, Bile Acid Sequestrants (Cholestyramine) | Reduced absorption of fat-soluble Vitamin D. | Moderate |
| Phenobarbital, Phenytoin, Carbamazepine | Induce hepatic CYP450 enzymes, increasing metabolism of Vitamin D to inactive compounds, reducing efficacy. | Moderate |
| Systemic Corticosteroids (e.g., Prednisolone) | Antagonize Vitamin D action, reducing calcium absorption. | Moderate |
| Cardiac Glycosides (Digoxin) | Hypercalcemia potentiates digoxin toxicity, increasing risk of arrhythmias. | Major |
| Lithium | Vitamin D may increase lithium levels and toxicity risk; monitor lithium levels. | Moderate |
| Calcium Supplements | Concomitant high-dose use increases risk of hypercalcemia and hypercalciuria. | Moderate |
7. Patient Counselling
- DO take this medicine exactly as prescribed, usually once a week/month.
- DO take it with your largest meal containing some fat (e.g., lunch/dinner with dal, vegetables cooked in oil, curd).
- DO ensure adequate dietary calcium intake (milk, curd, paneer, green leafy vegetables, ragi).
- DO inform your doctor if you are taking any other medicines, especially for blood pressure, seizures, or heart.
- DON'T take extra doses or take it daily unless instructed.
- DON'T start taking additional calcium or other vitamin D supplements without consulting your doctor.
- DON'T crush or chew the capsule.
8. Toxicology & Storage
Overdose: Symptoms of Vitamin D toxicity are those of hypercalcemia: Early: Nausea, vomiting, constipation, anorexia, polydipsia, polyuria, weakness, fatigue. Late: Confusion, psychosis, cardiac arrhythmias, renal failure, nephrocalcinosis, metastatic calcification (blood vessels, lungs, kidneys).
Storage: Store below 30°C. Protect from light and moisture. Keep the blister strips or bottle tightly closed. Keep out of reach of children. Do not freeze.