Pharmacology · Class
Immunoglobulins and antitoxins !
Ready-made antibodies, human or equine, that give immediate but temporary protection against a toxin, a virus or an antigen.
Updated 2026-11-01
What they are
Antibody products for passive immunisation: normal immunoglobulin (pooled from many donors), human hyperimmune immunoglobulins (tetanus, rabies, anti-D), equine antitoxins (diphtheria, botulism) and monoclonal antibodies (palivizumab, nirsevimab, anti-rabies).
Mechanism of action
The administered antibodies bind their antigen at once: they neutralise free toxins and viruses or, with anti-D, clear fetal red cells before the mother mounts her own response. They create no memory: protection lasts as long as the antibodies remain, longer for human IgG than for animal protein.
Target: Foreign antigens (toxins, viruses) or the RhD antigen on red cells
Drugs in this class
- Anti-D immunoglobulin (Rho(D))Human IgG against the RhD antigen. In an RhD-negative mother it clears RhD-positive fetal red cells before she forms…RhD antigen on fetal red cells
- Rabies immunoglobulinAntibodies against rabies virus that are infiltrated into the wound after severe exposures, while the vaccine builds…Rabies virus glycoprotein G
- Human tetanus immunoglobulinHuman IgG against tetanus toxin. It neutralises toxin not yet bound to nerves in tetanus-prone wounds and in the…Free tetanospasmin (tetanus toxin)
- Normal human immunoglobulin (IVIG)IgG pooled from the plasma of thousands of donors. It replaces antibodies in immunodeficiency and modulates the immune…Broad repertoire of antigens and Fc receptors
- Diphtheria antitoxin (equine)Horse antibodies that neutralise circulating diphtheria toxin. Given with antibiotics on clinical suspicion, without…Circulating diphtheria toxin
Others in the class
- Botulism antitoxin
- Equine rabies immunoglobulin
- Anti-rabies monoclonal antibodies
- Palivizumab
- Nirsevimab
Test yourself
Think of the answer, then tap the question to see it.
What is the main difference between passive and active immunisation?
Passive transfers ready-made antibodies: it protects at once but leaves no memory. Active (a vaccine) takes time to protect but builds lasting memory.
Why must an antitoxin be given early?
It only neutralises toxin circulating freely; toxin already bound to nerves or tissues cannot be removed.
Which late reaction is typical of horse antisera?
Serum sickness: immune complexes against the equine protein cause fever, urticaria, joint pain and lymph-node swelling days to weeks later.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: eEML - Electronic Essential Medicines List (World Health Organization, 2025); Farmacología básica y clínica (Katzung), ch. 55 (McGraw Hill, 2025); Farmacología básica y clínica (Katzung), appendix (vaccines and immune globulins) (McGraw Hill, 2025); Immune Globulin Intravenous (Human)(IVIG): MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025).
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Representative model, for educational purposes only.