Vitamin A Pharmacology

Vitamin A

About Vitamin A
Fat-soluble vitamin, Treatment of vitamin A deficiency.
Mechanism of Action of Vitamin A
Vitamin A is required for a variety of physiological functions in the body such as: - 1).Proper functioning of retina and formation of pigment Rhodopsin during dark adaptation. 2).promotes differentiation and maintains structural integrity of epithelia over the body and also retard the malignancies of epithelial structures.3).Promotes mucous secretion. 4).Inhibits keratinization, 5). Maintains proper bone growth, 6).Maintenance of spermatogenesis, 7).Supports foetal development, 8).Improves resistance to infection. It is required for proper antibody response, normal lymphocyte proliferation and killer cell function.
Pharmacokinets of Vitamin A
Absorption: Completely absorbed normally. Steatorrhoea, bile deficiency, and protein poor diet adversely affects the absorption and absorption requires bile salts, pancreatic lipase, and dietary fat.
Distribution: Stored primarily as palmitate in kupffer`s cells in liver. Circulates in the form of specific alpha-1 protein; retinol binding protein and transported to cellular retinol binding protein of target cells.
Metabolism: Metabolized in the liver.
Excretion: Excreted mainly through bile and a small amount is excreted through urine.
Onset of Action for Vitamin A
N/A
Duration of Action for Vitamin A
N/A
Half Life of Vitamin A
N/A
Side Effects of Vitamin A
Adverse effects occurs only with higher doses and toxicity
1. Nausea
2. Vomiting
3. Itching
4. Dermatitis
5. Exfoliation
6. Alopecia
7. Bone and joint pain
8. Anorexia
9. Irritability
10. Increased intracranial pressure
11. Hepatic impairment
12. Anaphylactic shock
Contra-indications of Vitamin A
1. Hypervitaminosis A
2. Hypersensitivity to the vitamin A
Special Precautions while taking Vitamin A
1. Oral form should not use in patients with malabsorption syndrome.
2. In inadequate bile secretion oral route may be used with concurrent administration of bile salts.
3. I. V. route is contraindicated except for special water miscible forms intended for infusion with large parenteral volumes and should not use I. V. push of vitamin A of any type.
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 A
1. Vitamin A deficiency
2. Xerophthalmia
3. Acne
4. Ichthyosis
5. Bitot`s spots
6. Night blindness
Interactions for Vitamin A
Cholestyramine: Absorption of Vitamin A is reduced due to reduced availability of fat stabilizing bile salts.
Mineral oil: Interferes with intestinal absorption of Vitamin A.
Oral Contraceptives: Plasma Vitamin A levels are significantly increased.
Typical Dosage for Vitamin A
Severe vitamin A deficiency with xerophthalmia: 500000 IU daily for 3 days followed by 50000 IU daily for 14 days. Then maintenance dosage of 10000 to 20000 IU for 2months followed by adequate dietary nutrition and RDA vitamin A supplements.
Severe vitamin A deficiency: 100000 IU daily for 3 days followed by 50000 IU daily for 14 days. Then maintenance dosage of 10000 to 20000 IU for 2months followed by adequate dietary nutrition and RDA vitamin A supplements.
Children: 5000 to 10000 IU daily for 14 days.
Schedule of Vitamin A
C1 (Oral)
C (Parenteral)
Storage Requirements for Vitamin A
Store in a well closed, airtight container in a cool dry place.
Effects of Missed Dosage of Vitamin A
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 A
Discontinue the vitamin A if hypercalcaemia persists and administer I.V. saline, prednisolone, and calcitonin if required. Monitor hepatic function tests to detect liver damage.

Home Delivery for Vitamin A 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 a.

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 a and other medicines and health products. Home delivery services for vitamin a 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 a 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 a before they complete the sale. You can get this information while placing the order for vitamin a with the pharmacy.

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