ascorbic acid (vitamin C)
Cecon, Cevi-Bid, Dull-C, Vita-C

Available forms
Available by prescription only
Injection: 500 mg/ml 50-ml vials
Capsules: 500 mg
Crystals: 120 g (4 g/teaspoon)
Liquid: 500 mg/5 ml
Lozenges: 60 mg
Powder: 120 g (4 g/teaspoon), 454 g (240 mg/teaspoon)
Solution: 100 mg/ml
Tablets: 100 mg, 250 mg, 500 mg, 1,000 mg
Tablets (chewable): 100 mg, 250 mg, 500 mg, 1,000 mg, 1,500 mg
Tablets (extended-release): 500 mg, 1,000 mg

Indications and dosages
 Recommended daily amount of ascorbic acid. Adults: 60 mg daily.
Smokers: 100 mg daily.
Pregnant women: 70 mg daily.
Breast-feeding women: 90 to 95 mg daily.
Infants and children: 30 to 60 mg daily.
Patients receiving long-term hemodialysis: 100 to 200 mg daily.
 Frank and subclinical scurvy. Adults: 100 to 250 mg, depending on severity, P.O., S.C., I.M., or I.V. daily or b.i.d.; then at least 50 mg daily for maintenance.
Infants and children: 100 to 300 mg, depending on severity, P.O., S.C., I.M., or I.V. daily; then at least 35 mg daily for maintenance.
 Prevention of ascorbic acid deficiency in those with poor nutritional habits or increased requirements. Adults: 45 to 60 mg P.O., S.C., I.M., or I.V. daily.
Pregnant or breast-feeding women: At least 60 to 80 mg P.O., S.C., I.M., or I.V. daily.
Children and infants older than age 2 weeks: At least 20 to 50 mg P.O., S.C., I.M., or I.V. daily.
 Potentiation of methenamine in urine acidification. Adults: 4 to 12 g daily in divided doses.
 Adjunctive therapy in the treatment of idiopathic methemoglobinemia. Adults: 300 to 600 mg P.O. daily in divided doses.
 Reduction of tyrosinemia in premature infants on high-protein diets. Premature infants: 100 mg P.O. or I.M. daily.
 To increase iron excretion resulting from deferoxamine administration. Adults: 100 to 200 mg P.O. daily.
 Prevention and treatment of the common cold. Adults: 1 to 3 g or more P.O. daily.

Pharmacodynamics
Nutritional action: Ascorbic acid, an essential vitamin, is involved with the biologic oxidations and reductions used in cellular respiration. It’s essential for the formation and maintenance of intracellular ground substance and collagen. In the body, ascorbic acid is reversibly oxidized to dehydroascorbic acid and influences tyrosine metabolism, conversion of folic acid to folinic acid, carbohydrate metabolism, resistance to infections, and cellular respiration. Ascorbic acid deficiency causes scurvy, a condition marked by degenerative changes in the capillaries, bone, and connective tissues. Restoring adequate ascorbic acid intake completely reverses symptoms of ascorbic acid deficiency. Data regarding use of ascorbic acid as a urinary acidifier are conflicting.

Pharmacokinetics
Absorption: After oral administration, ascorbic acid is absorbed readily. After very large doses, absorption may be limited because absorption is an active process. Absorption also may be reduced in patients with diarrhea or GI diseases. Normal plasma levels of ascorbic acid are about 10 to 20 mcg/ml. Plasma levels below 1.5 mcg/ml are linked to scurvy. However, leukocyte levels (although not usually measured) may better reflect ascorbic acid tissue saturation. About 1.5 g of ascorbic acid is stored in the body. Within 3 to 5 months of ascorbic acid deficiency, clinical signs of scurvy become evident.
Distribution: Distributed widely in the body, with large concentrations found in the liver, leukocytes, platelets, glandular tissues, and lens of the eye. Ascorbic acid crosses the placental barrier; cord blood levels are usually two to four times the maternal blood levels. Ascorbic acid is distributed into breast milk.
Metabolism: Metabolized in the liver.
Excretion: Reversibly oxidized to dehydroascorbic acid. Some is metabolized to inactive compounds that are excreted in urine. The renal threshold is about 14 mcg/ml. When the body is saturated and blood levels exceed the threshold, unchanged ascorbic acid is excreted in urine. Renal excretion is directly proportional to blood levels. Ascorbic acid is also removed by hemodialysis.

Contraindications and precautions
No known contraindications. Use cautiously in patients with renal insufficiency.

Interactions
Drug-drug. Acidic drugs in large doses (more than 2 g daily): May lower urine pH, causing renal tubular reabsorption of acidic drugs. Monitor patient for expected and adverse effects.
Basic drugs (such as amphetamines, tricyclic antidepressants): May cause decreased reabsorption and therapeutic effect. Monitor patient for expected and adverse effects.
Dicumarol: Influences intensity and duration of anticoagulant effect. Monitor PT and INR.
Ethinyl estradiol: May increase plasma ethinyl estradiol levels. Monitor these levels.
Iron: May increase iron absorption in GI tract, but this increase may not be significant. A combination of 30 mg of iron with 200 mg of ascorbic acid is sometimes recommended.
Salicylates: Inhibit ascorbic acid uptake by leukocytes and platelets. Watch for symptoms of ascorbic acid deficiency.
Sulfonamides: May cause crystallization. Avoid use together.
Warfarin: May inhibit anticoagulant effect. Monitor PT and INR.
Drug-lifestyle. Smoking: May decrease serum ascorbic acid level, thus increasing dosage requirements of this vitamin. Monitor patient closely.

Adverse reactions
CNS: faintness, dizziness (with too-rapid I.V. administration).
GI: diarrhea, GI discomfort.
GU: acid urine, oxaluria, renal calculi.
Skin: discomfort at injection site.

Effects on lab test results
None reported.

Overdose and treatment
Excessively high doses of parenteral ascorbic acid are excreted renally after tissue saturation and rarely accumulate. Serious adverse effects or toxicity are uncommon.
 Severe effects require discontinuation of therapy.

Special considerations
• Ascorbic acid is a strong reducing agent; it alters results of tests that are based on oxidation-reduction reactions. Large doses of ascorbic acid (more than 500 mg) may cause false-negative glucose determinations using the glucose oxidase method, or false-positive results using the copper reduction method or Benedict’s reagent.
• Ascorbic acid shouldn’t be used for 48 to 72 hours before an amine-dependent test for occult blood in the stool is conducted. A false-negative result may occur.
• Depending on the reagents used, ascorbic acid also may cause interactions with other diagnostic tests.
• Administer large doses of ascorbic acid (1,000 mg daily) in divided amounts because the body uses only a limited amount and excretes the rest in urine. Large doses may increase small intestine pH and impair vitamin B₁₂ absorption.
• Administer oral solutions of ascorbic acid directly into the mouth or mix with food.
• Administer I.V. solution slowly.
• Conditions that elevate the metabolic rate (hyperthyroidism, fever, infection, burns and other severe trauma, postoperative states, neoplastic disease, and chronic alcoholism) significantly increase ascorbic acid requirements.
• Prolonged use of large doses results in increased metabolism of ascorbic acid; scurvy may result when reduced to normal.
• Reportedly, patients taking hormonal contraceptives require ascorbic acid supplements.
• Smokers appear to have increased requirements for ascorbic acid because the vitamin is oxidized and excreted more rapidly than in nonsmokers.
• Use ascorbic acid cautiously in patients with renal insufficiency because the vitamin is normally excreted in urine.
• Patients whose diets are chemically deficient in fruits and vegetables can develop subclinical ascorbic acid deficiency. Observe for such deficiency in elderly and indigent patients, patients on restricted diets, those receiving long-term treatment with I.V. fluids or hemodialysis, and drug addicts or alcoholics.
• Symptoms of ascorbic acid deficiency include irritability; emotional disturbances; general debility; pallor; anorexia; sensitivity to touch; limb and joint pain; follicular hyperkeratosis (particularly on thighs and buttocks); easy bruising; petechiae; bloody diarrhea; delayed healing; loosening of teeth; sensitive, swollen, and bleeding gums; and anemia.
• Protect ascorbic acid solutions from light. Solution darkens with exposure to light, but this doesn’t impair the therapeutic activity of the drug. Ascorbic acid is incompatible with many drugs.
Pregnant patients
• Ingestion of large doses during pregnancy has resulted in scurvy in neonates.
Breast-feeding patients
• Administer cautiously to breast-feeding women because ascorbic acid appears in breast milk.
Pediatric patients
• Infants fed on cow’s milk alone require supplemental ascorbic acid.

Patient education
• Suggest good dietary sources of ascorbic acid, such as citrus fruits, leafy vegetables, tomatoes, green peppers, and potatoes.
• Instruct patient to cover foods and fruit juices tightly and to use them promptly.
• Advise patients with ascorbic acid deficiency to decrease or stop smoking. Replacement ascorbic acid dosages are greater for the smoker.
• Tell patient to avoid high doses of ascorbic acid if he is prone to renal calculi, has diabetes, is undergoing tests for occult blood in stools, follows a sodium-restricted diet, or takes an anticoagulant.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use