Vitamin D3 (Cholecalciferol) 300,000 IU is a high-dose, single-use oral or intramuscular formulation of the secosteroid hormone used for rapid correction of severe vitamin D deficiency. It is a prohormone that undergoes hepatic and renal hydroxylation to form the active metabolite calcitriol (1,25-dihydroxycholecalciferol), which regulates calcium and phosphate homeostasis, bone mineralization, and modulates immune function.
Adult: A single oral dose of 300,000 IU, repeated only after assessment of serum 25(OH)D levels (typically after 8-12 weeks). For severe deficiency, some protocols use 300,000 IU monthly for 2-3 months. Intramuscular: 300,000 IU as a single deep IM injection.
Note: ORAL: Administer the liquid/softgel capsule directly into the mouth or with a small amount of water. MUST be taken with or immediately after a meal containing fat (e.g., milk, curd, nuts) to maximize absorption. INTRAMUSCULAR: Administer as a deep IM injection, typically in the gluteal or deltoid muscle. Rotate sites if multiple doses are planned.
Vitamin D3 is a prohormone. After conversion to its active form, calcitriol, it 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, modulating their transcription.
Pregnancy: Category A (adequate studies show no risk). Vitamin D deficiency is common in pregnancy and supplementation is recommended. 300,000 IU can be used for treatment of documented severe deficiency under medical supervision. Routine high-dose use is not recommended.
Driving: No known effects. However, if hypercalcemia-induced drowsiness or confusion occurs, driving should be avoided.
| Thiazide Diuretics (e.g., Hydrochlorothiazide) | Increased risk of hypercalcemia due to reduced renal calcium excretion. | Major |
| Cardiac Glycosides (Digoxin) | Hypercalcemia may potentiate digitalis toxicity, leading to cardiac arrhythmias. | Major |
| Systemic Corticosteroids (e.g., Prednisolone) | May reduce the calcium-absorbing effects of vitamin D. | Moderate |
| Anticonvulsants (Phenytoin, Phenobarbital, Carbamazepine) | Increase hepatic metabolism of vitamin D to inactive compounds, reducing its efficacy. | Moderate |
| Orlistat, Cholestyramine | May reduce absorption of fat-soluble vitamin D. | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin) | May increase metabolism of vitamin D, reducing serum levels. | Moderate |
Same composition (Vitamin D3 (300000IU)), different brands: