Chemistry - Used systemically for cyanide or arsenic poisoning and topically as an antifungal, sodium thiosulfate occurs as large, colorless crystals or coarse, crystalline powder. It is very soluble in water, deliquescent in moist air and effloresces in dry air at temperatures >33°C.
Storage/Stability/Compatibility - Unless otherwise stated by the manufacturer, store at room temperature. Crystals should be stored in tight containers.
Pharmacology - By administering thiosulfate, an exogenous source of sulfur is available to the body, thereby allowing it hasten the detoxification of cyanide using the enzyme rhodanese. Rhodanese (thiosulfate cyanide sulfurtransferase) converts cyanide to the relatively nontoxic thiocyanate ion. Thiocyanate is then excreted in the urine.
Sodium thiosulfate’s topical antifungal activity is probably due to its slow release of colloidal sulfur.
While sodium thiosulfate has been recommended for treating arsenic (and some other heavy metal) poisoning, it’s proposed mechanism of action is not known. Presumably the sulfate moiety may react with and chelate the metal, allowing its removal.
Uses/Indications - Sodium thiosulfate (alone or in combination with sodium nitrite) is useful in the treatment of cyanide toxicity. It has been touted for use in treating arsenic or other heavy metal poisonings, but its efficacy is in question for these purposes. However, because sodium thiosulfate is relatively non-toxic and inexpensive, it may be tried to treat arsenic poisoning. When used in combination with sodium molybdate sodium thiosulfate may be useful for the treatment of copper poisoning.
Sodium thiosulfate may also be useful for the topical treatment for some fungal infections (Tinea). In humans, sodium thiosulfate has been used to reduce the nephrotoxicity of cisplatin therapy.
Pharmacokinetics - Sodium thiosulfate is relatively poorly absorbed from the GI tract. When substantial doses are given PO, it acts a saline cathartic. When administered intravenously, it is distributed in the extracellular fluid and then rapidly excreted via the urine.
Contraindications/Precautions/Reproductive Safety - There are no absolute contraindications to the use of the drug. Safe use during pregnancy has not been established; use when benefits outweigh the potential risks.
Adverse Effects/Warnings - The drug is relatively non-toxic. Large doses by mouth may cause profuse diarrhea. Injectable forms should be given slowly IV.
For cyanide toxicity: First give sodium nitrite at a dose of 16 mg/kg IV followed with a 20% solution of sodium thiosulfate given at a dose of 30 - 40 mg/kg IV. If repeating treatment, use sodium thiosulfate only. (Bailey and Garland 1992a)
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Sodium Thiosulfate for Injection 500 mg multidose vials, 300 mg/mL.Cya-dote Injection® (Anthony) (Rx). Approved for use in animal not to be used for food or lactating dairy animals.
Sodium Thiosulfate for Injection 25% (250 mg/ml) in 50 ml vials; Generic; (Rx)
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