Usage
Sodium thiosulfate is primarily used as an antidote for cyanide poisoning. It is also used in the management of calciphylaxis in patients undergoing hemodialysis, and to reduce the nephrotoxic and ototoxic side effects of cisplatin. It can also be used in the treatment of pityriasis versicolor. Its pharmacological classifications include antidote, chelating agent, and antioxidant.
Sodium thiosulfate works by detoxifying cyanide. It acts as a sulfur donor for the enzyme rhodanese, which converts cyanide to the less toxic thiocyanate, which is then excreted in the urine. In calciphylaxis, it is thought to chelate calcium and possibly act as a vasodilator and antioxidant.
Alternate Names
Sodium thiosulphate, disodium thiosulfate pentahydrate, hyposulphite of soda.
Brand name: Pedmark®.
How It Works
Pharmacodynamics: Sodium thiosulfate detoxifies cyanide by providing a sulfur atom for the conversion of cyanide to thiocyanate. In calciphylaxis, the mechanism isn’t completely understood but likely involves calcium chelation and potential vasodilation and antioxidant effects. For cisplatin ototoxicity, it reacts with cisplatin to form inactive platinum species and increases glutathione levels.
Pharmacokinetics: Administered intravenously, sodium thiosulfate is rapidly distributed throughout the extracellular fluid. It is primarily eliminated unchanged by the kidneys.
Mode of Action: Sodium thiosulfate donates sulfur to the mitochondrial enzyme rhodanese, which converts cyanide to thiocyanate. Thiocyanate is then excreted renally.
Elimination Pathways: Renal excretion.
Dosage
Standard Dosage
Adults:
- Cyanide poisoning: 12.5 g (50 mL of a 25% solution) IV infusion, administered over 10-20 minutes at a rate of 1.25 g/min (5 mL/min). May repeat at half the initial dose (6.25 g) if symptoms reappear.
- Cisplatin-induced ototoxicity (Pedmark®): 20 g/m² IV infusion over 15 minutes following cisplatin infusion.
Children:
- Cyanide poisoning: 250 mg/kg (1 mL/kg of 25% solution, maximum 12.5 g) IV, administered over at least 10 minutes at a rate of 2.5-5 mL/minute. Alternatively, a pediatric dose based on hemoglobin concentration may be used. May repeat at half the initial dose if symptoms reappear.
- Cisplatin-induced ototoxicity (Pedmark®): Not indicated.
Special Cases:
- Elderly Patients: No specific dosage adjustment. However, monitor renal function closely.
- Patients with Renal Impairment: Use with caution. Monitor for adverse effects. Dose reduction may be necessary.
- Patients with Hepatic Dysfunction: No specific dosage adjustment.
- Patients with Comorbid Conditions: Caution in patients with hypertension, edema, or sodium-retaining conditions (e.g., cirrhosis, congestive heart failure, toxemia of pregnancy).
Clinical Use Cases
Dosage recommendations typically follow the standard dosage as outlined above. Specific scenarios:
- Intubation/Surgical Procedures/Mechanical Ventilation/ICU Use: Standard cyanide antidote dosage if cyanide poisoning is suspected or confirmed.
- Emergency Situations (e.g., cyanide poisoning): Rapid administration of the standard cyanide antidote dosage.
Dosage Adjustments:
Adjustments may be needed based on renal function, recurrence of cyanide poisoning symptoms, or the presence of comorbid conditions.
Side Effects
Common Side Effects:
Nausea, vomiting, headache, hypotension (infusion rate-dependent), salty taste in mouth, warm sensation.
Rare but Serious Side Effects:
Hypersensitivity reactions (including anaphylaxis), severe hypotension, metabolic acidosis, hypernatremia, hypokalemia. Prolonged bleeding times with higher doses or infusions administered over 1-3 days.
Long-Term Effects:
Data is limited. Chronic complications from prolonged use are rare.
Contraindications
Known hypersensitivity to sodium thiosulfate.
Drug Interactions
Sodium thiosulfate may exhibit incompatibility with hydroxocobalamin and should not be administered simultaneously through the same IV line. Should not be co-administered with blood products through the same IV line. Caution advised with antihypertensives or medications that may cause hypotension.
Pregnancy and Breastfeeding
Pregnancy Safety Category: C. Use only if clearly needed. Data regarding excretion in breast milk are limited; caution advised. Cyanide and thiocyanate are present in human milk.
Drug Profile Summary
- Mechanism of Action: Sulfur donor for conversion of cyanide to thiocyanate.
- Side Effects: Nausea, vomiting, headache, hypotension, hypersensitivity.
- Contraindications: Hypersensitivity to sodium thiosulfate.
- Drug Interactions: Hydroxocobalamin, blood products.
- Pregnancy & Breastfeeding: Category C; use with caution.
- Dosage: See Dosage section above.
- Monitoring Parameters: Blood pressure, serum electrolytes, renal function.
Popular Combinations
Sodium nitrite is frequently used prior to sodium thiosulfate in the treatment of cyanide poisoning.
Precautions
Screen for sulfite allergies. Monitor for electrolyte imbalances (hypernatremia, hypokalemia) and metabolic acidosis, particularly in patients with pre-existing renal dysfunction, during Pedmark treatment. Pregnant and breastfeeding women should consult with a physician.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Sodium Thiosulphate in cyanide poisoning?
A: Adults: 12.5g IV over 10-20 minutes. Children: 250 mg/kg IV over at least 10 minutes (max 12.5g). Repeat at half the initial dose if necessary.
Q2: How does Sodium Thiosulphate work as a cyanide antidote?
A: It provides a sulfur donor for the enzyme rhodanese, facilitating conversion of cyanide to the less toxic thiocyanate.
Q3: What are the common side effects of Sodium Thiosulphate?
A: Nausea, vomiting, headache, and hypotension (related to infusion rate).
Q4: Are there any contraindications for using Sodium Thiosulphate?
A: Hypersensitivity to sodium thiosulfate.
Q5: Can Sodium Thiosulphate be used in pregnant or breastfeeding women?
A: Use with caution if benefits outweigh risks. Consult with a physician.
Q6: How is sodium thiosulfate administered?
A: Intravenous infusion.
Q7: What are the signs of cyanide toxicity?
A: Altered mental status, seizures, hypotension, lactic acidosis, and respiratory distress.
Q8: What is the role of Sodium Thiosulphate in calciphylaxis?
A: It’s used for its calcium-chelating, vasodilatory, and antioxidant properties.
Q9: What is the dose of Sodium Thiosulphate for calciphylaxis?
A: 25 g IV three times a week is commonly used.
Q10: How should Sodium Thiosulphate be administered with cisplatin?
A: 20 g/m² IV over 15 minutes following the cisplatin infusion.
