Sodium Thiosulfate

Sodium thiosulfate is a sulfur donor used principally in antidotal treatment of cyanide poisoning. Veterinary emergency applications include cyanogenic-plant exposure in ruminants. It also has selected specialist uses in toxicology and local tissue injury, although those applications have a smaller evidence base than its cyanide-detoxification role.

Group

Sulfur-donor antidote

Mechanism of Action

Thiosulfate supplies sulfur for sulfurtransferase pathways, including rhodanese-mediated conversion of cyanide to thiocyanate. This reduces cyanide available to inhibit mitochondrial cytochrome oxidase and permits recovery of cellular oxygen utilization. Thiocyanate is subsequently excreted. In selected local chemotherapy extravasations, chemical inactivation of reactive drug species provides a separate treatment rationale.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Cyanide antidote protocol	413 mg/kg	IV		Protocol dose, not stand-alone prescription: slow IV after separately prescribed sodium nitrite with monitoring of oxygen delivery and methemoglobinemia. Complete antidote selection and timing must be specified.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Cyanide antidote protocol	413 mg/kg	IV		Protocol dose, not stand-alone prescription: slow IV after separately prescribed sodium nitrite with monitoring of oxygen delivery and methemoglobinemia. Complete antidote selection and timing must be specified.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Cyanide antidote protocol	413 mg/kg	IV		Protocol dose, not stand-alone prescription: slow IV after separately prescribed sodium nitrite with monitoring of oxygen delivery and methemoglobinemia. Complete antidote selection and timing must be specified.
Alternative cyanide detoxification protocol	Reference only	IV		Described protocol uses sodium thiosulfate at least 500 mg/kg IV plus 30 g/cow PO for ongoing ruminal exposure. Select a complete emergency protocol; do not merge with the 413 mg/kg nitrite-following schedule.
Ruminal cyanide detoxification adjunct	Reference only	PO		30 g per cow orally has been described as an adjunct to the specified IV protocol. It does not replace systemic antidote therapy in a critically affected animal.
Alternative cyanogenic-plant poisoning regimen	660 mg/kg	IV	Once	Historical ruminant course using 30% solution. Rapid administration was described, while other instructions advise slow IV delivery; determine the actual rate in the complete emergency protocol before use.
Copper poisoning molybdate combination	Reference only	PO	Every 24 h	Up to 21 days; 500 mg sodium thiosulfate plus 200 mg ammonium or sodium molybdate total orally daily for up to 3 weeks, with fluid replacement. This is a fixed combination course, not an automatic single-active prescription.
Arsenic poisoning oral adjunct	Reference only	PO	Every 6 h	Up to 4 days; 30–60 g total every 6 hours for 3–4 days has been suggested, with fluid/electrolyte support; efficacy is uncertain. A separate IV amount of 30–60 g as a 10–20% solution was described without a repeat interval.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Cyanide antidote protocol	413 mg/kg	IV		Protocol dose, not stand-alone prescription: slow IV after separately prescribed sodium nitrite with monitoring of oxygen delivery and methemoglobinemia. Complete antidote selection and timing must be specified.
Alternative cyanogenic-plant poisoning regimen	660 mg/kg	IV	Once	Historical ruminant course using 30% solution. Rapid administration was described, while other instructions advise slow IV delivery; determine the actual rate in the complete emergency protocol before use.
Copper poisoning molybdate combination	Reference only	PO	Every 24 h	Up to 21 days; 500 mg sodium thiosulfate plus 200 mg ammonium or sodium molybdate total orally daily for up to 3 weeks, with fluid replacement. This is a fixed combination course, not an automatic single-active prescription.
Arsenic poisoning oral adjunct	Reference only	PO	Every 6 h	Up to 4 days; 30–60 g total every 6 hours for 3–4 days has been suggested, with fluid/electrolyte support; efficacy is uncertain. A separate IV amount of 30–60 g as a 10–20% solution was described without a repeat interval.

Goats

Use / stage	Dose	Route	Schedule	Instructions
Cyanide antidote protocol	413 mg/kg	IV		Protocol dose, not stand-alone prescription: slow IV after separately prescribed sodium nitrite with monitoring of oxygen delivery and methemoglobinemia. Complete antidote selection and timing must be specified.
Alternative cyanogenic-plant poisoning regimen	660 mg/kg	IV	Once	Historical ruminant course using 30% solution. Rapid administration was described, while other instructions advise slow IV delivery; determine the actual rate in the complete emergency protocol before use.
Copper poisoning molybdate combination	Reference only	PO	Every 24 h	Up to 21 days; 500 mg sodium thiosulfate plus 200 mg ammonium or sodium molybdate total orally daily for up to 3 weeks, with fluid replacement. This is a fixed combination course, not an automatic single-active prescription.
Arsenic poisoning oral adjunct	Reference only	PO	Every 6 h	Up to 4 days; 30–60 g total every 6 hours for 3–4 days has been suggested, with fluid/electrolyte support; efficacy is uncertain. A separate IV amount of 30–60 g as a 10–20% solution was described without a repeat interval.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Arsenic poisoning adjunct	Reference only	PO		20–30 g total in 300 mL water orally with dimercaprol 3 mg/kg IM q4h has been described. Evidence for arsenic benefit is uncertain; timing and hydration require a complete toxicology plan.
Historical cyanide nitrite-following course	Reference only	IV		After sodium nitrite 16 mg/kg IV (another course uses 10–20 mg/kg IV as a 20% solution), give sodium thiosulfate 30–40 mg/kg IV as a 20% solution. If repeated, give thiosulfate alone. This historical amount is much lower than other cyanide courses; do not merge the ranges.

Indications

Treatment of cyanide poisoning, including selected cyanogenic-plant intoxication in ruminants, within an emergency antidote protocol.
Specialist local treatment of selected platinum-drug extravasation injuries, with limited veterinary clinical evidence.
Selected combination treatment with molybdate for copper poisoning in sheep, with protocol-specific evidence.

Contraindications

Hypersensitivity

Interactions

Do not give hydroxocobalamin simultaneously through the same IV line because of chemical incompatibility.
Do not run blood products and sodium thiosulfate simultaneously through the same IV line.
Reported incompatibility with cyanocobalamin; do not admix.

Adverse effects

Vomiting
Hypotension with IV administration
Profuse diarrhea after large oral doses

Toxicity

Excessive or rapid administration can disturb circulation and acid-base balance; monitor and provide supportive care.

Preparations

Preparation	Form	Strength	Route
Sodium thiosulfate injection 25% w/v 250 mg/mL for the specified medicinal formulation. Select a complete cyanide antidote protocol; do not assume compatibility with other antidotes.	Injection	250 mg / mL	IV
Sodium thiosulfate injection 10% w/v 100 mg/mL as pentahydrate; no assumed conversion to anhydrous salt.	Injection	100 mg / mL	IV

Monitoring and Administration

Provide airway, ventilation, oxygen and circulatory support while treating suspected cyanide exposure.

One veterinary protocol gives 413 mg/kg IV slowly after sodium nitrite. Another describes at least 500 mg/kg IV plus 30 g per cow orally to reduce ongoing ruminal cyanide release. These are different protocols and are not one broad dose range.

Nitrite use requires assessment of methemoglobinemia and oxygen delivery; some smoke-inhalation settings require a different antidote choice.

The older sheep study tested different thiosulfate/nitrite exposures; experimental doses are not substituted for a complete clinical protocol.

Monitor blood pressure and oxygenation. Store the described 250 mg/mL injection at 20–25°C, protected from light; do not freeze.

Large oral doses can cause profuse diarrhea. In arsenic or copper exposure, thiosulfate is an adjunct with uncertain arsenic efficacy; do not delay established poisoning management.

Human-derived extravasation approaches include a 2% SC solution with corticosteroids for anthracyclines, or 0.17 mol/L solution for cisplatin/carboplatin. A cited preparation combines 4 mL of 10% pentahydrate solution with 6 mL sterile water; 5 mL infiltration was described for carboplatin. These are not validated universal dog/cat protocols and must not be substituted for a drug-specific extravasation plan.

Historical ruminant withdrawal advice suggested 24 hours, but no current local authorization is inferred. Do not mix with cyanocobalamin; keep the already specified hydroxocobalamin incompatibility separate.