Vitamin D3 Pharmacology

Vitamin D3

About Vitamin D3
Mechanism of Action of Vitamin D3
Vitamin D3 is a form of vitamin D. It is also called as Cholecalciferol.7-Dehydrocholesterol is the precursor of vitamin D3 and only forms the vitamin after being exposed to UV radiation.After exposure to the sun, cholecalciferol is sent to the liver to be hydroxylated where it becomes 25-Hydroxyvitamin D3.Next, it is sent to the kidney and once again hydroxylated becoming 1,25-Hydroxyvitamin D3. 1,25-Hydroxyvitmain D3 is the active form of vitamin D3, for this reason vitamin D is often referred to as a prohormone.Vitamin D exerts it`s action by influencing calcium homoeostasis. It increases the intestinal absorption of calcium and phosphate. It binds to the cytoplasmic Vitamin D receptor and translocates to the nucleus and thus increases the synthesis of specific m RNA and regulates protein synthesis. It increases the synthesis of a carrier protein for calcium called "calbindin" or calcium binding protein. Activation of Vitamin D receptor enhances endocytotic capture of calcium and it`s transport across duodenal mucosal cells in a vesicular form. Vitamin D promotes resorption of calcium and phosphate from bone by enhancing recruitment and differentiation of osteoclast precursors in the bone remodeling units. It helps in bone mineralization.
Pharmacokinets of Vitamin D3
Absorption: Well absorbed orally in the presence of bile salts, Malabsorption and steatorrhoea interfere with it`s absorption.
Distribution: Widely distributed in a protein bound form. It is stored in adipose tissue and liver.
Metabolism: It is hydroxylated in to both active and inactive metabolites and also metabolized in kidney.
Excretion: Metabolites are excreted mainly through bile.
Onset of Action for Vitamin D3
Duration of Action for Vitamin D3
Half Life of Vitamin D3
Side Effects of Vitamin D3
1. Hypercalcaemia
2. Fatigue
3. Weakness
4. Diarrhoea
5. Vomiting
6. Sluggishness
7. Albuminuria
8. Polyuria
9. Calcification of soft tissues (blood vessels, parenchymal organs including heart)
10. Arrhythmias
11. Renal stones
12. Growh retardation in children
13. Hypertension
14. Anorexia
15. Nausea
16. Constipation
17. Elevated liver enzymes
Contra-indications of Vitamin D3
1. Hypercalcaemia
2. Hypervitaminosis D
3. Renal osteodystrophy with hyperphosphatemia
4. Renal impairment
Special Precautions while taking Vitamin D3
1. Renal diseases
2. Renal stones
3. Cardiac diseases
4. Arteriosclerosis
5. Coronary diseases
Pregnancy Related Information
Use with caution
Old Age Related Information
Use with caution
Breast Feeding Related Information
Use with caution
Children Related Information
Use with caution
Indications for Vitamin D3
1. Rickets and Osteomalacia
2. Hypoparathyroidism
3. Fanconi`s syndrome
4. Osteoporosis
Interactions for Vitamin D3
Antacids: Hypermagnesemia may develop in patients on renal dialysis who take magnesium containing antacids.
Digitalis glycosides: May precipitate cardiac arrhythmias due to hypercalcemia.
Verapamil: Atrial fibrillation may occur.
Cholestyramine: Intestinal absorption of Vitamin D may be reduced.
Mineral Oil: Prolonged use of mineral oil may result in reduced absoprtion of Vitamin D.
Phenytoin, Barbiturates: Half life of vitamin D may be reduced.
Thaizide diuretics: Hypoparathyroid patients on Vitamin D may develop hypercalcemia due to thiazide diuretics.
Typical Dosage for Vitamin D3
Nutritional Rickets and Osteomalacia: 25 to 125mcg daily in normal gastrointestinal absorption. In severe malabsorption; 250mcg to 7.5mg orally or 250mcg I.M.
Vitamin dependent Rickets: 250mcg to 1.5mg daily
Hypoparathyroidism: 625mcg to 5mg daily with calcium supplements
Fanconi`s syndrome: 1.25 to 5mg daily
Osteoporosis: 25 to 250mcg daily or 1.25mg once weekly with calcium and fluoride supplements.
Hypophosphatemia: 250mcg to 1.5mg along with phosphate supplements
Nutritional Rickets and Osteomalacia: 25 to 125mcg daily in normal gastrointestinal absorption. In severe malabsorption; 250mcg to 625mcg orally
Vitamin dependent Rickets: 75 to 125mcg daily.
Fanconi`s syndrome: 625mcg to 1.25mg daily
Hypophosphatemia: 1 to 2mg daily with phosphate supplements. Increase the dose in increments of 250 to 500mcg at intervals of 3 to 4months until desired therapeutic response is obtained.

Schedule of Vitamin D3
Storage Requirements for Vitamin D3
Store in a well closed container in a cool place. Protect from light and excess heat. Keep out of reach of children.
Effects of Missed Dosage of Vitamin D3
Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Continue the regular schedule. Do not double the dose.
Effects of Overdose of Vitamin D3
Provide supportive and symptomatic treatment. Stops the treatment and starting a low calcium diet. Increases the fluid intake and administer Loop diuretics like furosemide may be given with saline I.V. infusion to increase calcium excretion. Calcitonin may decrease hypercalcaemia.

Home Delivery for Vitamin D3 in Your City

Medicine India is just a publishing medium for medicine related information and does not provide services or sales of medicines including vitamin d3.

However, we do publish a comprehensive directory of Pharmacies, Chemists and Druggists in cities all over India. You can use this directory to find the medicine stores in your city (or area) that provide home delivery services for vitamin d3 and other medicines and health products. Home delivery services for vitamin d3 may be free or they may cost you depending on the pharmacy and the minimum order requirements. It would be best to get this clarified while placing the order.

Please be aware that you should take vitamin d3 only if a doctor has recommended or prescribed it. Some or all pharmacies who provide a home delivery service for medicines might insist on a prescription for vitamin d3 before they complete the sale. You can get this information while placing the order for vitamin d3 with the pharmacy.

Vitamin D3 is a generic medicine name and there are several brands available for it. Some of the brands for vitamin d3 might be better known than vitamin d3 itself. If the pharmacy that's willing to deliver medicines to your home doesn't have vitamin d3 in stock, you can ask for one of the branded alternatives for vitamin d3.