What are the guidelines for administering intravenous (IV) vitamin C?

Guidelines for Administering Intravenous (IV) Vitamin C

IV vitamin C should be administered at a dose of 2-3 g per day during critical illness and acute inflammation, diluted with normal saline or glucose to minimize adverse reactions. 1

Dosing Recommendations by Clinical Scenario

Critical Illness

• During critical illness, a higher vitamin C repletion dose of 2-3 g per day should be given IV during the acute phase of inflammation 1
• For patients on continuous renal replacement therapy (CRRT), 2-3 g/day IV is recommended 1
• For periprocedural repletion in cardiac surgery, 1-2 g/day for 5-7 days IV is recommended 1

Specific Clinical Conditions

• For sepsis, high-dose vitamin C with thiamine and hydrocortisone has been proposed, though recent evidence suggests limited mortality benefit 1, 2
• For severe sepsis and acute respiratory failure, some protocols have used 200 mg/kg/day of vitamin C for 4 days 1
• For patients with chronic oxidative stress (diabetes mellitus, smoking, heart failure, alcoholism, severe COPD, chronic dialysis) or malabsorption, a dose of 200-500 mg/day may be provided 1

Administration Guidelines

Preparation and Dilution

• For IV injection, vitamin C should be diluted with normal saline or glucose to minimize adverse reactions 1
• For adults and children age 11 years and above, the contents of one vial can be dissolved in 10 ml of appropriate solution 3
• For children below 11 years of age, dosing should be weight-based with children weighing less than 10 kg receiving 1/10 of the content of one vial per kg body weight per day 3

Stability

• IV vitamin C solutions (1.5 g per 50 mL of 0.9% saline and 2.5 g per 50 mL of D5W) remain stable for up to 96 hours and do not need to be protected from light 4
• The concentration of vitamin C in diluted solutions decreases less than 10% by 96 hours both at 4°C in the dark and at ambient temperature and light 4

Monitoring and Safety Considerations

Contraindications and Cautions

• Caution should be exercised in patients with renal dysfunction, glucose-6-phosphate dehydrogenase deficiency, hemochromatosis, kidney stones, or oxaluria 5
• Vitamin C plasma levels decline rapidly with progressive inflammation, making interpretation of levels difficult during critical illness 1
• Blood levels decrease as soon as CRP >10 mg/L, and normal values are not detected if CRP >40 mg/L 1

Measurement Recommendations

• Plasma vitamin C concentrations may be measured in patients with clinical suspicion of scurvy or chronic low intake 1
• Measurement of plasma vitamin C is not recommended in critical illness or severe inflammation due to the difficulty in interpretation of results 1
• If clinical symptoms of deficiency are present, a clinical trial of vitamin C of about 1 g/day for at least one week should not be delayed 1

Evidence Quality and Clinical Efficacy

• The recommendation for IV vitamin C during critical illness (2-3 g/day) has a Grade B recommendation with 84% consensus 1
• Recent evidence suggests that IV vitamin C probably does not substantially impact mortality at 90 days in sepsis patients 2
• IV vitamin C may result in a slight reduction in duration of vasopressor support but may not reduce sequential organ failure assessment scores 2
• High-dose IV vitamin C appears to be remarkably safe, with mostly minor side effects reported including lethargy/fatigue, changes in mental status, and vein irritation/phlebitis 6

Practical Considerations

• In critically ill patients, IV administration is crucial as enteral uptake is unpredictable due to limited enteral transporter capacity and often impaired gut function 1
• Sustained therapy is needed to prevent recurrence of hypovitaminosis 1
• For vitamin C deficiency treatment, IV vitamin C may be administered when malabsorption is suspected 1