Hydroxocobalamin
Hydroxocobalamin
Brand names:Cyanokit
A vitamin B12 precursor used as the first-line antidote for cyanide poisoning. Hydroxocobalamin binds free cyanide ions to form cyanocobalamin (vitamin B12), which is then renally excreted. Cyanokit is the formulation used in emergency response for smoke inhalation, fire-related cyanide exposure, and industrial cyanide poisoning.
Pharmacology and Actions
Hydroxocobalamin contains a cobalt ion that binds cyanide with high affinity, forming cyanocobalamin (vitamin B12), a non-toxic compound excreted in urine. Each molecule of hydroxocobalamin binds one molecule of cyanide. The conversion is rapid and does not produce methemoglobinemia (in contrast to nitrite-based cyanide antidotes), making hydroxocobalamin safer in smoke inhalation casualties who may already have impaired oxygen-carrying capacity from carbon monoxide co-exposure.
Indications
- Known or suspected cyanide poisoning from industrial exposure
- Smoke inhalation with altered mental status, hypotension, severe acidosis, or elevated lactate (clinical markers of cyanide co-toxicity)
- Fire-related cyanide exposure (residential and commercial fire smoke contains hydrogen cyanide from combustion of synthetic materials)
- Iatrogenic cyanide toxicity from prolonged sodium nitroprusside infusion
Absolute Contraindications
- Known hypersensitivity to hydroxocobalamin
- No absolute contraindications in life-threatening cyanide exposure
Precautions and Side Effects
Red discoloration of skin, mucous membranes, and urine for 2 to 28 days (cosmetic, not harmful, but can interfere with colorimetric lab assays for up to 24 hours). Transient hypertension common (peaks 15 minutes after infusion). Allergic reactions including rash, urticaria, anaphylaxis (rare). Photosensitivity. Acneiform eruption. May interfere with hemodialysis machine sensors.
Adult Dosing
Pediatric Dosing
70 mg/kg IV (max 5 g) infused over 15 minutes. May repeat once based on severity (max cumulative 140 mg/kg or 10 g).
Pharmacokinetics
Peak Effect: End of infusion
Duration: Plasma half-life approximately 26 to 31 hours
Storage and Handling
Room temperature 15 to 30 degrees C in original packaging; protect from light. Cyanokit comes as a 5 g vial of powder for reconstitution; shelf life typically 3 years. Once reconstituted, use within 6 hours.
Reconstitution:
Reconstitute 5 g vial with 200 mL of 0.9% sodium chloride (Lactated Ringer or D5W acceptable if NS unavailable). Invert and rock vial for at least 1 minute to mix; do not shake (causes foaming). Solution is dark red. Administer through 200 mL IV bag or directly via vial connector if supplied with kit.
TCCC and TECC Role
Not a core TCCC trauma medication. Standard component of fire department EMS protocols for smoke inhalation. Carried by hazmat and tactical EMS teams responding to industrial accidents and fire scenes. The 2026 NFPA 1584 and most state EMS protocols include hydroxocobalamin for empiric treatment of suspected cyanide toxicity in smoke inhalation casualties with altered mental status or hemodynamic instability.
Hydroxocobalamin is what changed fire-rescue medicine. For decades, smoke inhalation casualties with altered mental status were treated as carbon monoxide exposure alone. We now know that residential and commercial fires produce substantial hydrogen cyanide from burning synthetic materials, and that cyanide is often the proximate cause of death in fire fatalities. Empiric hydroxocobalamin administration in any fire casualty with altered mental status, hypotension, or severe acidosis is now standard of care. The drug is expensive (several thousand dollars per dose) but the operational threshold for administration is low because the downside of unnecessary administration is minor cosmetic discoloration while the downside of withholding from a true cyanide casualty is death.
Withholding hydroxocobalamin until cyanide poisoning is confirmed. Confirmation requires lab assays that take hours; the casualty needs the antidote within minutes. The standard of care is empiric administration based on clinical suspicion (smoke inhalation plus altered mental status, hypotension, severe acidosis, or elevated lactate above 8 mmol/L). The other common mistake is relying solely on hydroxocobalamin without managing the airway, oxygenation, and carbon monoxide co-exposure that typically accompany cyanide toxicity in fire casualties.
This drug profile is provided as educational reference material for trained medical providers. It is not medical advice, not a substitute for formal training, and not a substitute for current published guidelines or medical direction.
Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances are subject to additional handling, accountability, and documentation requirements per DEA and state law. Always verify dosing, indications, contraindications, and route of administration against current published guidelines and your local protocols before administration.
If this content is being viewed during a medical emergency, call 911 immediately and follow the direction of your local emergency dispatch and medical control. Do not use this reference as a substitute for emergency medical services.
Drug information evolves. Last reviewed dates and source citations are provided for each entry. Confirm currency against the cited source before clinical use.
Penn Tactical Solutions publishes this reference for educational purposes. PTS does not provide medical direction and does not assume responsibility for clinical decisions made in the field. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Educational reference for trained medical providers. Not medical advice. Not a substitute for formal training, current published guidelines, or medical direction. Drug administration is governed by your scope of practice, agency standing orders, medical director protocols, and applicable state and federal regulations. Controlled substances require additional storage, accountability, and documentation per DEA and state law.
In a medical emergency, call 911. This reference is not a substitute for emergency medical services.
Verify dosing, indications, and contraindications against current published guidelines and your local protocols before administration. Confirm content currency against the source citation. Penn Tactical Solutions does not provide medical direction. Clinical responsibility rests with the administering provider, their medical director, and their agency.
Hydroxocobalamin
| IV/IO | 5 g IV infused over 15 minutes (single dose). May repeat 5 g IV over 15 minutes to 2 hours based on severity (total 10 g maximum in most protocols). Cyanokit is supplied as a 5 g powder reconstituted with 200 mL of 0.9% sodium chloride. (Within minutes) |
| IM | None (not given IM) (None) |
| IN | None (None) |
| PO | None (None) |