Beta-carotene, retinol, and retinal have effective and reliable vitamin A activity. Retinal and retinol are in chemical equilibrium in the body and have equivalent antixerophthalmic activity. Retinal combines with the rod pigment, opsin, in the retina to form rhodopsin, necessary for visual dark adaptation.
Vitamin A prevents retardation of growth and preserves the epithe-lial cells' integrity. Normal adult liver storage is sufficient to satisfy two years'requirements of vitamin A. Vitamin A is readily absorbed from the gastrointestinal tract, where the biosynthesis of vitamin A from beta-carotene takes place. Vitamin A absorption requires bile salts, pancreatic lipase, and dietary fat. It is transported in the blood to the liver by the chy lomicron fraction of the lymph. Vitamin Ais stored in Kupffer cells of the liver mainly as the palmitate. Normal serum vitamin A is 80-300 Units per 100 mL (plasma range is 30-70 mcg per dl) and for carotenoids 270-753 Units per 100 mL.The normal adult liver contains approximately 100 to 300 micrograms per gram, mostly as retinol palmitate.
Illness due to vitamin A deficiency in ophthalmology such as night blindness, xerophthalmia and dermatological such as changes in skin, hair and nails. Concomitant therapy of mucosa illnesses such as sinusitis, bronchitis, in acne vulgaris, ichthyosis, Darier's disease, psoriasis etc. To meet vitmin A demand in growth, resistance to infections and night blindness. This is also indicated to meet vitamin A deficiency after diarrhoea and prophylaxis of measles.
Vitamin A intoxication includes irritability, vomiting, loss of appetite, headache, dry and pruritic skin, skin desquamation, fatique, pain in ankles and feet, myalgia, loss of body hair, papilledema, nystagmus, liver sclerosis and cirrhosis.
Safety of amounts exceeding 6,000 Units of vitamin A daily during pregnancy has not been established at this time. The use of vitamin A in excess of the recommended dietary allowance may cause fetal harm when administered to a pregnant woman. Animal reproduction studies have shown fetal abnormalities associated with over-dosage in several species. Malformations of the central nervous system, the eye, the palate, and the urogenital tract are recorded. Vitamin Ain excess of the recommended dietary allowance is contraindicated in women who are or may become pregnant. If vitamin Ais used during pregnancy, or if the patient becomes pregnant while taking vitamin A, the patient should be apprised of the potential hazard to the fetus.
The U.S. Recommended Daily Allowance (RDA) of vitamin A (5,000 Units) is recommended for nursing mothers.
Ensure Vitamin A free interval after long term therapy with vitamin A. No daily dose over 5000 IU during pregnancy. Vitamin A doses over 50000 IU under medical supervision only.
Vitamin-A preparations
Keep below 25°C temperature, away from light & moisture. Keep out of the reach of children.
