Diphtheria antitoxin

How it works

It provides passive immunity by supplying preformed antibodies that bind and neutralise unbound diphtheria toxin before it enters host cells.

Prescribing in practice

• As a product of equine origin it carries a substantial risk of anaphylaxis and serum sickness, so administer with facilities for managing severe allergic reactions and follow recommended hypersensitivity-testing procedures.
• It neutralises only circulating toxin and does not act on toxin already bound to tissues, so it should be given as early as possible on clinical suspicion without waiting for laboratory confirmation.
• Appropriate antibacterial therapy and public-health notification are required alongside antitoxin, as it does not eradicate the organism.

Monitoring

Monitor closely for immediate hypersensitivity during and after administration and observe for delayed serum sickness over subsequent days.

Counselling the patient

• This treatment is given urgently in hospital because diphtheria toxin can cause serious harm if not neutralised early.
• Close contacts will need assessment and preventive measures from public-health services.

Evidence & guidelines

Use is directed by UK Health Security Agency guidance on the management of diphtheria, reflecting established clinical and public-health practice.