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.
Ascorbic acid should not be ingested 48—72 hours before amine-dependent stool occult blood tests are conducted because false negatives may occur.
Chronic, excessive doses of ascorbic acid can cause an increase in its own metabolism, which can cause scurvy if normal and supplemental intake are significantly reduced or discontinued. Large doses can also increase the likelihood of oxalate stones in the urinary tract in patients with a history of nephrolithiasis, hyperoxaluria, or oxalosis.
Large IV or oral doses of ascorbic acid have caused hemolytic anemia in some patients with G6PD deficiency (glucose-6-phosphate dehydrogenase deficiency).
High doses of ascorbic acid may interfere with urinary glucose determinations using the glucose oxidase method. Patients with diabetes mellitus should be made aware of the possibility of falsely decreased glucose concentrations with these tests.
Ascorbic acid may increase the risk of iron toxicity in patients with hemochromatosis, therefore, patients with hemochromatosis should limit their intake of ascorbic acid to no more than 500 mg/day. Rarely, ingestion of large quantities of ascorbic acid have been associated with fatal cardiac arrhythmias in patients with iron overload.
Patients with anemia (e.g., sideroblastic anemia, thalassemia) may experience decreased iron absorption during high dose ascorbic acid therapy. High doses of ascorbic acid may precipitate a crisis in patients with sickle cell anemia.
Ascorbic acid, vitamin C is classified as pregnancy category C. Umbilical cord blood concentrations are 2—4 times higher than those of maternal plasma levels. Adverse effects have not been reported with the normal daily intake of ascorbic acid, vitamin C within the recommended dietary daily intakes for a pregnant female. The use of ascorbic acid, vitamin C in excess of the recommended dietary allowance during normal pregnancy should be avoided unless, in the judgment of the physician, potential benefits in a specific, unique case outweigh the significant hazards involved. 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.
Ascorbic acid, vitamin C is distributed into breast milk. Use of ascorbic acid, vitamin C within the recommended daily dietary intake for lactating women is generally recognized as safe. In mothers not taking vitamin C supplements, vitamin C in human milk in the first 6 months of lactation varied from 34—83 mg/L. In mothers taking vitamin C supplements ranging from 45 to > 1,000 mg/day, vitamin C content of human milk varied from 45—115 mg/L. 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. Consider the benefits of breastfeeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breastfeeding infant experiences an adverse effect related to a maternally administered drug, healthcare providers are encouraged to report the adverse effect to the FDA.
Ascorbic acid is necessary for many physiologic functions, including the metabolism of iron. Cenolate® (ascorbic acid, vitamin C injection) package insert. North Chicago, IL: Abbott Laboratories; 2002 Sept. The absorption of nonheme iron (primarily from plant sources) from the intestinal tract depends on iron being in its reduced form. (Heme iron, found in meat, fish, and poultry, appears to be absorbed intact.) Ascorbic acid, by maintaining iron in the ferrous state, can enhance the absorption of oral iron, however, the magnitude of this increase is in the range of 10% and only occurs with doses of ascorbic acid, vitamin C of 500 mg or greater. Healthy individuals usually absorb iron supplements (e.g., iron salts or polysaccharide-iron complex) adequately from the GI tract, but some patients may benefit from receiving supplemental ascorbic acid with each oral iron dose.
Patients should be advised not to take ascorbic acid, vitamin C supplements along with deferoxamine chelation therapy unless such supplements are prescribed with the approval of their health care professional. Patients with iron overload usually become vitamin C deficient, probably because iron oxidizes the vitamin. Vitamin C can be a beneficial adjunct in iron chelation therapy because it facilitates iron chelation and iron complex excretion. As an adjuvant to iron chelation therapy (e.g., deferoxamine), vitamin C (in doses up to 200 mg/day for adults, 50 mg/day in children < 10 years of age or 100 mg/day in older children) may be given in divided doses, starting after an initial month of regular treatment with deferoxamine. However, higher doses of ascorbic acid, vitamin C can facilitate iron deposition, particularly in the heart tissue, causing cardiac decompensation. In patients with severe chronic iron overload, the concomitant use of deferoxamine with > 500 mg/day PO of vitamin C in adults has lead to impairment of cardiac function; the dysfunction was reversible when vitamin C was discontinued. The manufacturer of deferoxamine recommends certain precautions for the coadministration of vitamin C with deferoxamine. First, vitamin C supplements should not be given concurrently with deferoxamine in patients with heart failure. Secondly, in other patients, such supplementation should not be started until 1 month of regular treatment with deferoxamine, and should be given only to patients receiving regular deferoxamine treatments. Do not exceed vitamin C doses of 200 mg/day for adults, 50 mg/day in children < 10 years of age, or 100 mg/day in older children, given in divided doses. Clinically monitor all patients, especially the elderly, for signs or symptoms of decreased cardiac function.Desferal® (deferoxamine mesylate for injection USP) package insert. East Hanover, NJ: Novartis Pharmaceuticals Corporation; 2002 Oct.
Oxalate, urate, or cystine renal stones causing renal tubular obstruction, characterized by costovertebral pain or lower back pain, can occur following large doses of ascorbic acid. Hyperoxaluria develops in 5% of patients taking large doses. Patients at an increased risk are those with renal disease, on hemodialysis, or with a history of nephrolithiasis.Sestili MA: Possible adverse health effects of vitamin C and ascorbic acid. Semin Oncol. 1983;10:299.
Ascorbic acid is generally nontoxic. Adverse reactions that have been reported include flushing, headache, nausea/vomiting, and abdominal cramps. Diarrhea has resulted from oral dosages of more than 1 gram daily. Dizziness and faintness can result from rapid administration of IV ascorbic acid.Sestili MA: Possible adverse health effects of vitamin C and ascorbic acid. Semin Oncol. 1983;10:299.
Hemolytic anemia due to hemolysis has been observed in some patients with glucose 6-phosphate dehydrogenase (G6PD) deficiency after receiving large IV or oral doses of ascorbic acid. In rare cases, sickle-cell crisis has occurred in patients with sickle cell disease because of decreased blood pH.Campbell GD, Steinberg MH, Bower JD. Ascorbic acid-induced hemolysis in G-6-PD deficiency. Ann Int Med 1975;82(6):810. Letter.
Excessive use of chewable ascorbic acid formulations can lead to dental caries or sensitivity from the breakdown of dental enamel. Hays GL, Bullock Q, Lazzari EP, Puente ES. Salivary pH while dissolving vitamin C-containing tablets. Am J Dent. 1992;5:269-271.
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.
