Tetanus Antitoxin [Equine]

Approved Indications:

• Post-exposure prophylaxis of tetanus: In individuals with tetanus-prone wounds who have not been previously immunized with tetanus toxoid, or whose immunization history is incomplete or uncertain.
• Treatment of clinical tetanus: As part of the therapeutic regimen for individuals with established tetanus infection to neutralize unbound tetanus toxin.

Clinically Accepted Off-label Uses:

• Prophylaxis in mass casualty or disaster settings with high risk of contaminated wounds in unvaccinated populations.
• Prophylactic use in veterinary medicine for treatment of tetanus-prone wounds in livestock (not applicable for human use but relevant to origin and sourcing of equine antitoxin).

Route of Administration: Intramuscular (IM) injection

Prophylaxis:

• Adults & Children ≥7 years: 1,500–3,000 IU IM once, depending on wound severity and immunization history.
• Children <7 years: Dose based on body weight; typically 750–1,500 IU IM once.

Treatment of Clinical Tetanus:

• Adults: 10,000–20,000 IU IM once, preferably as early as possible.
• Children: 3,000–6,000 IU IM once, adjusted by weight and severity.

Special Populations:

• Elderly: No dosage adjustment required solely based on age; monitor for hypersensitivity.
• Renal/Hepatic Impairment: No specific dose adjustment recommended; monitor for immune reactions due to equine origin.

Administration Notes:

• Always perform a hypersensitivity (intradermal) test dose before full administration.
• Epinephrine and resuscitative equipment should be available during administration.
• Do not administer intravenously.
• Administer tetanus toxoid concurrently (but in separate sites) if prophylaxis is required.

Tetanus Antitoxin [Equine] provides passive immunization by supplying preformed antibodies (immunoglobulins) derived from horse serum that bind to and neutralize circulating tetanus neurotoxin (tetanospasmin). These antibodies prevent the neurotoxin from binding to nerve terminals, thereby halting its progression toward the central nervous system. The antitoxin does not reverse toxin effects already bound to neurons but can prevent further binding, reducing severity and fatality in clinical tetanus and offering immediate, though temporary, protection in post-exposure settings.

• Absorption: Rapid after intramuscular injection; passive antibodies enter systemic circulation within hours.
• Distribution: Systemic distribution, particularly in areas of vascular injury or infection; does not cross the blood-brain barrier.
• Metabolism: Catabolized by the reticuloendothelial system as a foreign protein (equine origin).
• Elimination Half-life: Approximately 10–23 days.
• Excretion: Via kidneys and hepatic degradation pathways.

• Pregnancy: Classified as Category C (FDA); animal reproduction studies have not been conducted with equine-derived antitoxins. Use only if clearly needed and benefits outweigh potential risks.
• Lactation: Unknown if excreted in human milk; caution advised. Risk of sensitization or allergic reaction in the breastfed infant is extremely low.
• Note: Limited data available; passive immunity may be beneficial in high-risk maternal tetanus exposures.

• Primary Class: Passive Immunizing Agent
• Subclass: Antitoxins – Equine-derived Biological Products

• Known hypersensitivity to equine (horse) serum or components of the formulation.
• History of anaphylaxis or severe allergic reactions to heterologous serum.
• Previous serum sickness reaction to equine antitoxin.
• Do not use intravenously or via alternate routes other than specified.

• Hypersensitivity reactions: Anaphylaxis, serum sickness, urticaria, bronchospasm; test dosing required.
• Delayed serum sickness may occur 7–14 days post-injection.
• Monitor closely post-injection for 30–60 minutes, especially after the first dose.
• Pre-sensitization testing (intradermal) is mandatory before full administration.
• Use with caution in patients with asthma, autoimmune disease, or immunodeficiency.
• Concurrent toxoid immunization is essential for long-term protection, as antitoxin does not induce active immunity.

Common (≥1%):

• Local pain and swelling at injection site
• Fever
• Rash
• Headache

Less Common:

• Urticaria
• Arthralgia
• Nausea, vomiting

Serious (Rare):

• Anaphylaxis (rapid onset; life-threatening)
• Serum sickness (fever, rash, arthralgia occurring days to weeks after administration)
• Hypotension
• Bronchospasm

Onset: Immediate (hypersensitivity) or delayed (serum sickness); dose-independent.

• Immunosuppressants (e.g., corticosteroids, chemotherapy): May reduce efficacy of antibody response.
• Live vaccines (especially MMR or varicella): Delay administration for at least 6 weeks post-antitoxin, as antibodies may interfere with vaccine efficacy.
• No major CYP450 enzyme interactions known.
• No food or alcohol interactions of clinical significance reported.

• WHO and CDC guidelines emphasize the continued role of Tetanus Antitoxin [Equine] in settings where human tetanus immunoglobulin (TIG) is not available.
• FDA advisory recommends informed consent for use due to risk of hypersensitivity and availability of human-derived alternatives in developed settings.
• Updated protocols support co-administration with tetanus toxoid vaccine and antibiotic wound care for comprehensive post-exposure prophylaxis.

• Storage Temperature: Store at 2°C to 8°C (Refrigerated). Do not freeze.
• Light Protection: Keep vials in the original outer carton to protect from light.
• Handling: Shake gently before use. Inspect for particulate matter or discoloration before administration.
• Stability: Use immediately after opening. Do not reuse any remaining solution.