Vit D

# Vit d ## Overview - **Classification**: Fat-soluble vitamin, Secosteroid hormone precursor - **Mechanism**: Metabolized to calcitriol, which regulates calcium and phosphate homeostasis, bone metabolism, and cellular growth/differentiation. ## Primary Indications 1. **Vitamin D Deficiency/Insufficiency**: Treatment and prevention of low vitamin D levels. 2. **Osteoporosis**: Adjunct therapy to improve bone mineral density and reduce fracture risk. 3. **Hypoparathyroidism**: Management of hypocalcemia. ## Adult Dosing ### Standard Dosing **Vitamin D Deficiency (25(OH)D < 20 ng/mL)** - **Dose**: **50,000 IU** (ergocalciferol or cholecalciferol) - **Frequency**: Once weekly - **Route**: Oral - **Duration**: 8-12 weeks, then re-evaluate. - **Alternative for deficiency**: **6,000 IU** (cholecalciferol) once daily. **Vitamin D Insufficiency (25(OH)D 20-30 ng/mL)** - **Dose**: **1,000-2,000 IU** (cholecalciferol) - **Frequency**: Once daily - **Route**: Oral **Maintenance/Prevention** - **Dose**: **800-2,000 IU** (cholecalciferol) - **Frequency**: Once daily - **Route**: Oral ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment for parent vitamin D (D2/D3). Monitor levels closely. Active vitamin D metabolites (e.g., calcitriol) are used in severe CKD. - **Hepatic Impairment**: No specific dose adjustment. Consider malabsorption with severe cholestatic liver disease; may require higher doses or parenteral. - **Elderly Patients**: May have reduced skin synthesis and dietary intake; generally follow adult dosing but ensure adequate supplementation for bone health. ## Pediatric Dosing ### Neonates (0-28 days) - **Indication**: Prevention of deficiency (all breastfed or partially breastfed infants). - **Dose**: **400 IU** (cholecalciferol) - **Frequency**: Once daily - **Maximum**: **400 IU/day** - **Special Notes**: Liquid drops are standard formulation. ### Infants (1-12 months) - **Indication**: Prevention of deficiency. - **Dose**: **400 IU** (cholecalciferol) - **Frequency**: Once daily - **Maximum**: **1,000 IU/day** for prevention (up to 2,000 IU/day for treatment of deficiency under medical supervision). ### Children (1-12 years) - **Indication**: Prevention of deficiency. - **Dose**: **600-1,000 IU** (cholecalciferol) - **Frequency**: Once daily - **Maximum**: **2,000-4,000 IU/day** (prevention, up to 5,000 IU/day for treatment of deficiency under medical supervision). ### Adolescents (13-18 years) - **Indication**: Prevention of deficiency. - **Dose**: **600-1,000 IU** (cholecalciferol) - **Frequency**: Once daily - **Maximum**: Up to **4,000 IU/day** (often approach adult dosing for deficiency treatment). ## Safety Information ### Contraindications - **Absolute**: Hypercalcemia (calcium > 10.5 mg/dL) - **Absolute**: Malabsorption syndrome (unless treated) - **Absolute**: Evidence of vitamin D toxicity - **Relative**: Hyperphosphatemia (caution, may worsen) ### Common Adverse Effects - **Very Common (>10%)**: Generally well-tolerated at recommended doses. - **Common (1-10%)**: Nausea, vomiting, constipation, polyuria (usually with toxicity). - **Serious but Rare**: Hypercalcemia (with excessive dosing), nephrolithiasis, kidney damage (due to prolonged hypercalcemia). ### Key Drug Interactions - **Corticosteroids**: May decrease vitamin D effects; consider higher doses. - **Phenytoin, Carbamazepine, Barbiturates**: Increase vitamin D metabolism, potentially leading to deficiency. - **Cholestyramine, Colestipol, Orlistat**: May reduce vitamin D absorption; administer vitamin D at least 2 hours before or after. - **Thiazide Diuretics**: May increase risk of hypercalcemia; monitor calcium. - **Cardiac Glycosides (e.g., Digoxin)**: Hypercalcemia due to vitamin D can potentiate digoxin toxicity; monitor closely. ## Monitoring & Follow-up - **Before Treatment**: Baseline 25(OH)D, serum calcium, phosphorus, PTH, renal function (Cr). - **During Treatment**: Recheck 25(OH)D, serum calcium, phosphorus 8-12 weeks after starting high-dose therapy, then periodically (e.g., every 3-6 months). - **Clinical Signs**: Monitor for symptoms of hypercalcemia: nausea, vomiting, constipation, polyuria, weakness, confusion. ## Clinical Pearls - 💡 **Optimal Level**: Aim for 25(OH)D levels between **30-60 ng/mL** for most individuals. - 💡 **Fat-soluble**: Take vitamin D with a meal containing fat to enhance absorption. - 💡 **Source**: Cholecalciferol (D3) is generally preferred over ergocalciferol (D2) due to higher potency and longer half-life. - 💡 **Supplementation for all**: Infants should receive vitamin D supplementation regardless of diet (breastfed or formula-fed). > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.