What is the recommended intravenous (IV) dosage of hydroxocobalamin for treating cyanide poisoning?

Hydroxocobalamin Dosage for Cyanide Poisoning

The recommended intravenous (IV) dosage of hydroxocobalamin for treating cyanide poisoning in adults is 5 g initially, with a second 5 g dose (total 10 g) for cardiac arrest or severe cases. 1

Adult Dosing Protocol

• Initial dose: 5 g IV for suspected cyanide poisoning 1
• Additional dosing:
  • For cardiac arrest: Administer a second 5 g dose (total 10 g) 1
  • For severe poisoning with blood cyanide levels >40 μmol/L: Consider a second 5 g dose 2, 3
• Administration: Given as an IV infusion

Pediatric Dosing Protocol

• Initial dose: 70 mg/kg IV (maximum 5 g) 1
• Indications for use in children:
  • Moderate cyanide poisoning: GCS score 13, confusion, stridor, hoarse voice, polypnea, dyspnea, soot particles in airways 1
  • Severe cyanide poisoning: GCS score ≤8, seizures, coma, mydriasis, severe hemodynamic disorders, collapse, respiratory depression 1

Clinical Decision Making

When to Administer Hydroxocobalamin

Hydroxocobalamin should not be administered routinely after smoke inhalation but reserved for:

1. Adult patients with smoke inhalation AND high suspicion of severe cyanide poisoning 1

   • Cardiac or respiratory arrest
   • Shock
   • Coma
   • Plasma lactate ≥8 mmol/L (strong indicator of cyanide toxicity) 1, 4

2. Children with smoke inhalation AND signs of moderate to severe cyanide poisoning 1

Combination Therapy

• Add sodium thiosulfate: Reasonable to administer in addition to hydroxocobalamin to enhance cyanide elimination 1, 5
• Administer 100% oxygen: Reasonable to provide alongside antidote therapy 1

Efficacy and Safety Considerations

• Hydroxocobalamin is the primary recommended treatment for cyanide poisoning due to its favorable safety profile 1, 4
• Survival rates of 67-71% have been reported in patients with confirmed cyanide poisoning treated with hydroxocobalamin 6, 3
• A single 5 g dose appears capable of binding all available cyanide for blood concentrations up to approximately 40 μmol/L 2

Common Side Effects

• Chromaturia (red-colored urine)
• Pink or red skin discoloration
• Transient hypertension
• Erythema

Important Caveats

1. Timing is critical: Administer as soon as possible after suspected exposure
2. Laboratory interference: Hydroxocobalamin may interfere with certain laboratory tests due to its red color
3. Monitoring: Closely monitor acid-base status, as normalization of lactic acidosis can indicate treatment efficacy
4. Avoid delay: Do not delay administration while waiting for confirmation of cyanide levels in suspected severe cases
5. Smoke inhalation: Consider combined carbon monoxide and cyanide poisoning in fire victims, which may require additional interventions

Hydroxocobalamin is preferred over other cyanide antidotes (like sodium nitrite) in smoke inhalation victims due to its safety profile and lack of adverse effects on oxygen-carrying capacity 4.