Sodium Thiosulfate
Sodium thiosulfate is a versatile antidote primarily used in veterinary medicine for **cyanide** and **arsenic** poisoning. * **Cyanide Toxicity**: Often used alone or in combination with sodium nitrite. * **Heavy Metal Poisoning**: Used for arsenic or copper poisoning (with sodium molybdate), though efficacy for arsenic is debated. * **Chemotherapy Extravasation**: Used to mitigate tissue damage from extravasation of cisplatin, carboplatin, dactinomycin, and doxorubicin. * **Topical Use**: Occasionally used for fungal infections (Tinea). > **Clinical Pearl**: Because it is relatively non-toxic and inexpensive, it is a staple in emergency toxicology kits, especially for large animals exposed to cyanogenic plants.
Mechanism: Sodium thiosulfate acts primarily as an exogenous sulfur donor. * **Cyanide Antidote**: It provides sulfur to the enzyme **rhodanese** (thiosulfate cyanide sulfurtransferase). Rhodanese catalyzes the conversion of highly toxic cyanide โ relatively non-toxic **thiocyanate** ion, which is then safely excreted in the urine. * **Heavy Metal Chelation**: The sulfate moiety is presumed to react with and chelate metals like arsenic, facilitating their removal from the body. * **Topical Antifungal**: Activity is likely due to the slow release of colloidal sulfur.
Dosing by species
- Copper poisoning ยท 500 mg sodium thiosulfate in combination with 200 mg ammonium or sodium molybdate PO daily ยท PO ยท q24h ยท up to 3 weeks ยท Ruminant dose. In conjunction with fluid replacement therapy
- Cyanide toxicity secondary to cyanogenic plants ยท 660 mg/kg IV sodium thiosulfate in a 30% solution given rapidly using a 12 or 14 gauge needle. ยท IV ยท Once ยท Ruminant dose.
- Arsenic poisoning ยท 30-60 grams PO every 6 hours for 3-4 days and 30-60 grams as a 10-20% solution IV ยท PO/IV ยท q6h ยท 3-4 days ยท Ruminant dose. Adjunctive fluid and electrolyte replacement is necessary.
- Copper poisoning ยท 500 mg sodium thiosulfate in combination with 200 mg ammonium or sodium molybdate PO daily ยท PO ยท q24h ยท up to 3 weeks ยท Ruminant dose. In conjunction with fluid replacement therapy
- Cyanide toxicity secondary to cyanogenic plants ยท 660 mg/kg IV sodium thiosulfate in a 30% solution given rapidly using a 12 or 14 gauge needle. ยท IV ยท Once ยท Ruminant dose.
- Arsenic poisoning ยท 30-60 grams PO every 6 hours for 3-4 days and 30-60 grams as a 10-20% solution IV ยท PO/IV ยท q6h ยท 3-4 days ยท Ruminant dose. Adjunctive fluid and electrolyte replacement is necessary.
- Cyanide toxicity ยท Contact an animal poison control center for guidance. ยท IV ยท As directed ยท As directed
- Doxorubicin extravasation ยท Subcutaneous sodium thiosulfate 2% added to therapy with subcutaneous hydrocortisone and topical betamethasone ยท SC ยท Once ยท Human recommendation extrapolated for veterinary use
Routes of administration
Contraindications
- None absolute
Adverse effects
- Profuse diarrhea (with large oral doses)
Drug interactions
- Cyanocobalamin ยท Not compatible when mixed together
Monitoring
- Clinical efficacy (resolution of toxicity signs)
- Hydration status (if diarrhea occurs from oral dosing)
Overdose
The drug is relatively non-toxic. Large doses by mouth may cause profuse diarrhea. Injectable forms should be given slowly IV.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.