Sodium thiosulfate

#completed #carded

Related FACEM curriculum (2022) learning objectives:

• ME 3.8.1.6(e) Principles of management of toxicological presentations including: Indications for antidotes
• ME 3.8.2.4 Identify the appropriate antidote or antivenom.

Presentation

• Sodium thiosulfate 12.5 g/50 mL vials.

Toxicological Indications

• Suspected cyanide poisoning.
• Potential use for poisoning by other substances such as:
  • Chlorate
  • Cisplatin
  • Bromate
  • Bromine
  • Iodine
  • Mustard gas
  • Nitrogen mustard

Contraindications

• None: Low toxicity at recommended doses.

Mechanism of Action

• Enhances cyanide detoxification by donating sulfur for the enzyme rhodanese, which converts cyanide to thiocyanate, a non-toxic compound. This process supports the body's natural detoxification capacity.

Pharmacokinetics

• Distribution: Rapidly disperses in the extracellular space; limited distribution to the brain.
• Excretion: Mostly unchanged via renal excretion; elimination half-life of 0.5–3 hours.
• Metabolism: Minor oxidation to sulfate through a hepatic process.

Administration

• Ensure patient is in a monitored setting with full resuscitative support.
• Administer 12.5 g IV (50 mL of 25% solution) over 10 minutes or 200 mg/kg IV over 10 minutes.
• Repeat dose after 30 minutes if cyanide toxicity symptoms persist.

Therapeutic Endpoints

• Improvement in consciousness.
• Haemodynamic stability.
• Correction of metabolic acidosis.

Adverse Drug Reactions

• Generally mild and less significant than the dangers of cyanide poisoning itself.
• Rapid injection may cause nausea and vomiting.
• Other potential minor effects include hypotension, headache, abdominal pain, and disorientation due to thiocyanate production.

Specific Considerations

• Pregnancy: Safety not established; use if clinically necessary.
• Paediatrics: Recommended dose is higher at 400 mg/kg compared to adults.

Handy Tips

• Collect blood for cyanide level before administering the antidote.
• Sodium thiosulfate, combined with oxygen and supportive care, may be sufficient for treating mild to moderately severe cyanide poisoning.
• It can be beneficial for uncertain cases, like smoke inhalation, providing both diagnostic and therapeutic value.
• In severe cyanide toxicity, use with other antidotes for a synergistic effect.

Controversy

• No clinical trials confirm its efficacy in humans. Sodium thiosulfate has a relatively slow onset and may be considered a second-line treatment for acute cyanide poisoning.