ascorbic acid: clinical use

Prescribing considerations

• Confirm deficiency and investigate its dietary, absorptive or clinical cause.
• Prefer oral or dietary replacement when feasible; parenteral products are licensed where oral replacement is unsuitable or difficult.
• Assess renal function, oxalate-stone risk, G6PD status and iron-overload history before parenteral or substantial replacement.
• Account for lactose in the selected tablet and sodium in the concentrated infusion product.

Contraindications and cautions

• Hypersensitivity to ascorbic acid or formulation excipients.
• Hyperoxaluria; the concentrated infusion is also contraindicated in oxalate urolithiasis.
• For the concentrated infusion: severe renal impairment, iron-storage or iron-overload disorders and G6PD deficiency.
• The concentrated infusion is contraindicated in children under 12 years.

Monitoring

• Renal function and evidence of oxalate crystalluria or stones in at-risk patients.
• Haemolysis in people with known or suspected G6PD deficiency.
• Cardiac function when used with desferrioxamine.
• Clinical response and relevant laboratory markers, accounting for analytical interference.

Clinical pharmacology

A water-soluble electron donor and enzyme cofactor. Oral absorption is transporter-mediated and becomes less efficient as intake increases; excess absorbed ascorbate and metabolites are predominantly cleared through the kidneys. Intravenous administration produces substantially higher plasma concentrations than oral administration.

Formulation and product differences

• The selected oral tablet contains lactose; its score line is for easier swallowing, not equal division.
• The standard injection is a ready solution for parenteral administration, contains sodium metabisulphite and requires refrigerated storage.
• The concentrated infusion is adult-only, preservative-free, high in sodium, requires dilution and must be administered by a physician; unused solution is discarded after opening.

Tablet

Route: Oral

Strengths: 500 mg

Injection

Route: Parenteral

Strengths: 150 mg/mL, 500 mg/5 mL