General Information
Ascorbic acid is a water-soluble vitamin found in fruits and vegetables such as citrus fruits and green peppers. It occurs as a white or slightly yellow crystal or powder with a slight acidic taste. It is an antiscorbutic product. On exposure to air and light it gradually darkens. In the dry state it is reasonably stable in air, but in solution it rapidly oxidizes. Ascorbic acid is a free radical, an antioxidant scavenger, and plays a major role in oxidation-reduction reactions. Ascorbic acid is a cofactor for enzymes involved in the biosynthesis of collagen (essential for tissue maintenance and repair), carnitine, and neurotransmitters. Humans cannot synthesize ascorbic acid endogenously and a lack of dietary intake can lead to scurvy. Vitamin C is most frequently used as a nutritional supplement. It also is used as an adjunct treatment of idiopathic methemoglobinemia and with deferoxamine in the treatment of chronic iron toxicity. Ascorbic acid has been used for a variety of ailments including the common cold, gum infections, acne, depression, fertility, and cancer; however, these claims have not been substantiated and vitamin C is not recommended for these purposes (see Mechanism of Action). Ascorbic acid was approved by the FDA in 1939.
Mechanism of Action
Ascorbic acid is necessary for collagen formation (e.g., connective tissue, cartilage, tooth dentin, skin, and bone matrix) and tissue repair. It is reversibly oxidized to dehydroascorbic acid. Both forms are involved in oxidation-reduction reactions. Vitamin C is involved in the metabolism of tyrosine, carbohydrates, norepinephrine, histamine, and phenylalanine. Other processes that require ascorbic acid include biosynthesis of corticosteroids and aldosterone, proteins, neuropeptides, and carnitine; hydroxylation of serotonin; conversion of cholesterol to bile acids; maintenance of blood vessel integrity; and cellular respiration. Vitamin C may promote resistance to infection by the activation of leukocytes, production of interferon, and regulation of the inflammatory process. It reduces iron from the ferric to the ferrous state in the intestine to allow absorption, is involved in the transfer of iron from plasma transferrin to liver ferritin, and regulates iron distribution and storage by preventing the oxidation of tetrahydrofolate. Ascorbic acid enhances the chelating action of deferoxamine during treatment of chronic iron toxicity (see Interactions). Vitamin C may have a role in the regeneration of other biological antioxidants such as glutathione and α-tocopherol to their active state.
Ascorbate deficiency lowers the activity of microsomal drug-metabolizing enzymes and cytochrome P-450 electron transport. In the absence of vitamin C, impaired collagen formation occurs due to a deficiency in the hydroxylation of procollagen and collagen. Non-hydroxylated collagen is unstable, and the normal processes of tissue repair cannot occur. This results in the various features of scurvy including capillary fragility manifested as hemorrhagic processes, delayed wound healing, and bony abnormalities.
Currently, the use and dosage regimen of vitamin C in the prevention and treatment of diseases, other than scurvy, is unclear. Although further study is needed to recommend vitamin C therapy for the following ailments, recent data indicate a positive role for vitamin C for: overall increased mortality; the prevention of coronary heart disease (especially in women); management of diabetes mellitus; reducing the risk of stroke; management of atherosclerosis in combination with other antioxidants; osteoporosis prevention; reducing the risk of Alzheimer disease in combination with vitamin E; and the prevention of cataracts. In humans, an exogenous source of ascorbic acid is required for collagen formation and tissue repair.
Storage
Store this medication in a refrigerator at 36°F to 46°F (2°C to 8°C). Keep all medicines out of the reach of children. Throw away any unused medicine after the beyond use date. Do not flush unused medications or pour down a sink or drain.
References
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- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes – Panel on Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids and the Subcommittee on Upper Reference Levels of Nutrients, Food and Nutrition Board, Institute of Medicine (IOM). Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. 2000.The National Academy of Sciences Press, Washington DC.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes – Panel on Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids and the Subcommittee on Upper Reference Levels of Nutrients, Food and Nutrition Board, Institute of Medicine (IOM). Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. 2000.The National Academy of Sciences Press, Washington DC.
- Cenolate® (ascorbic acid, vitamin C injection) package insert. North Chicago, IL: Abbott Laboratories; 2002 Sept.
- Desferal® (deferoxamine mesylate for injection USP) package insert. East Hanover, NJ: Novartis Pharmaceuticals Corporation; 2002 Oct.
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