Diphtheria Antitoxin (Equine)

What it is and how it works

Purified equine immunoglobulin (or its fragments) obtained from horses hyperimmunised with diphtheria toxin. It neutralises circulating, unbound diphtheria toxin but cannot reverse toxin already bound to tissues, so it must be given as early as possible.

Indications

Treatment of suspected or confirmed diphtheria (respiratory or cutaneous with systemic toxicity), given as early as possible together with appropriate antibiotics.

Dosage and administration (summary)

Dosing is individualised by the specialist according to the site and extent of membrane, duration of illness and toxicity, given intravenously (or intramuscularly in mild cases) after sensitivity testing, according to protocol.

Contraindications

No absolute contraindication in confirmed diphtheria; patients with known hypersensitivity to equine proteins require desensitisation under close supervision.

Warnings and precautions

Anaphylaxis and serum sickness (typically 7–14 days after administration) can occur because of the equine origin; a sensitivity test should precede administration and adrenaline and resuscitation facilities must be immediately available. Not used for prophylaxis of contacts.

Pregnancy

May be used when clinically indicated, as untreated diphtheria poses greater risk.

Storage and supply

Store refrigerated at 2–8 °C; do not freeze.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.