Drug information of Vitamin C

Mechanism of effect

In humans, an exogenous source of ascorbic acid is required for collagen formation and tissue repair by acting as a cofactor in the posttranslational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins. Ascorbic acid is reversibly oxidized to dehydroascorbic acid in the body. These two forms of the vitamin are believed to be important in oxidation-reduction reactions.

The vitamin is involved in tyrosine metabolism, conversion of folic acid to folinic acid, carbohydrate metabolism, synthesis of lipids and proteins, iron metabolism, resistance to infections, and cellular respiration.

Pharmacodynamic

Pharmacokinetics

• Absorption

70% to 90%

• Volume of distribution

Not Available

• Protein binding

25%

• Metabolism

Hepatic. Ascorbic acid is reversibly oxidised (by removal of the hydrogen from the enediol group of ascorbic acid) to dehydroascorbic acid. The two forms found in body fluids are physiologically active. Some ascorbic acid is metabolized to inactive compounds including ascorbic acid-2-sulfate and oxalic acid.

• Route of elimination

Not Available

• Half life

16 days (3.4 hours in people who have excess levels of vitamin C)

• Clearance

Not Available

Dosage

Adults:

Dosage Forms

tablets

• 100mg
• 250mg
• 500mg
• 1g

chewable, tablet

• 100mg
• 250mg
• 500mg

capsule, extended release

• 500mg

tablet, extended release

• 500mg
• 1000mg
• 1500mg

crystals

• 120g
• 480g

granules

• 100g
• 500g
• 1000g

injectable solution

• 250mg/mL
• 500mg/mL

oral solution

• 100mg/mL

powder effervescent

• 150g

powder, oral

• 113mg
• 120mg
• 480mg

water, oral

• 500mg

syrup, oral

• 100mg/mL

RDA

Males: 90 mg/day

Females: 75 mg/day

Pregnant: 85 mg/day; not to exceed 2000 mg/day (80 mg if <18 years; not to exceed 1800 mg/day)

Nursing: 120 mg/day; not to exceed 2000 mg/day (115 mg if <18 years old; not to exceed 1800 mg/day)

Urinary Acidification

4-12 g/day PO/IV divided three or four times daily

Ascorbic Acid Deficiency (Scurvy)

Oral prevention: See recommended daily intake

Oral treatment: 250 mg PO QID x 1 week

Treatment with IV ascorbic acid

• Indicated for short term (<1 week) treatment of scurvy in adult and children ≥5 months for whom oral administration is not possible, insufficient, or contraindicated
• 200 mg IV qDay; recommended daily treatment should not exceed 7 days
• If no improvement in scorbutic symptoms, retreat until resolution of scorbutic symptoms is observed 

Pediatric

Dosage Forms & Strengths

tablets

• 100mg
• 250mg
• 500mg
• 1g

chewable, tablet

• 100mg
• 250mg
• 500mg

capsule, extended release

• 500mg

tablet, extended release

• 500mg
• 1000mg
• 1500mg

crystals

• 120g
• 480g

granules

• 100g
• 500g
• 1000g

injectable solution

• 250mg/mL
• 500mg/mL

oral solution

• 100mg/mL

powder effervescent

• 150g

powder, oral

• 113mg
• 120mg
• 480mg

water, oral

• 500mg

syrup, oral

• 100mg/mL

RDA

0-6 months: 40 mg/day

6-12 months: 50 mg/day

1-3 years: 15 mg/day

3-8 years: 25 mg/day

8-13 years: 45 mg/day

13-18 years: (male) 75 mg/day; (female) 65 mg/day

UL: 1-3 years: 400 mg/day; 4-8 years old: 600 mg/day; 9-13 years old: 1.2 g/day; 12-18 years old: 1.8 g/day

Urinary Acidification

500 mg/day divided PO/IV TID/QID

Ascorbic Acid Deficiency (Scurvy)

Oral prevention: See recommended daily intake

Oral treatment, infants or children: 100 mg PO TID x 1 week, then 100 mg PO qDay until resolved (typically 1-3 months)

Treatment with IV ascorbic acid

• Indicated for short term (<1 week) treatment of scurvy in children and adolescents ≥5 months for whom oral administration is not possible, insufficient or contraindicated
• <5 months: Safety and efficacy not established
• 5 months to <12 months: 50 mg IV qDay
• 1 year to <11 years: 100 mg IV qDay
• ≥11 years: 200 mg IV qDay; recommended daily treatment should not exceed 7 days
• If no improvement in scorbutic symptoms, retreat until resolution of scorbutic symptoms is observed
• Repeat dosing is not recommended in children and adolescents <11 years

Interactions

Alerts

Cautions

Hemolysis has been reported with ascorbic acid in patients with glucose-6-phosphate dehydrogenase deficiency; discontinue treatment if hemolysis is suspected and treat as needed

Ascorbic acid may interfere with laboratory tests based on oxidation-reduction reactions (eg, blood and urine glucose testing, nitrite and bilirubin levels, and leucocyte count testing); delay laboratory tests until 24 hours after ascorbic acid infusion if possible

Oxalate nephropathy and nephrolithiasis

• Acute and chronic oxalate nephropathy reported with prolonged administration of high doses of ascorbic acid
• Increased risk for oxalate nephropathy in patients with renal disease, renal impairment, history of oxalate kidney stones, and geriatric patients
• Monitor renal function; discontinue treatment if oxalate nephropathy develops and treat any suspected oxalate nephropathy accordingly

Drug interactions overview

• Ascorbic acid may decrease effects of erythromycin, kanamycin, streptomycin, doxycycline, and lincomycin; if antibiotic efficacy is suspected, discontinue ascorbic acid
• Limited case reports have suggested interference of ascorbic acid with anticoagulation effects of warfarin; monitor
• Amphetamine and other drugs affected by urine pH
• Ascorbic acid may acidify urine
• Lowers amphetamines levels by increasing renal excretion
• May alter excretion of certain drugs affected by urine pH (eg, fluphenazine)

Points of recommendation

Use exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

The recommended dietary allowance of vitamin C (Vitamin C) increases with age. Follow your healthcare provider's instructions.

Drink plenty of liquids while you are taking Vitamin C.

The chewable tablet must be chewed before you swallow it.

Vitamin C gum may be chewed as long as desired and then thrown away.

Do not crush, chew, or break an extended-release tablet. Swallow it whole.

Measure liquid medicine with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

Keep the orally disintegrating tablet in the package until you are ready to take it. Use dry hands to remove the tablet and place it in your mouth. Do not swallow the tablet whole. Allow it to dissolve in your mouth without chewing. Swallow several times as the tablet dissolves.

Store Vitamin C at room temperature away from moisture and heat.

Do not stop using Vitamin C suddenly after long-term use at high doses, or you could have "conditional" vitamin C deficiency. Symptoms include bleeding gums, feeling very tired, and red or blue pinpoint spots around your hair follicles. Follow your doctor's instructions about tapering your dose. Conditional vitamin C deficiency can be difficult to correct without medical supervision.

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