Hydroxocobalamin (High-Dose — Cyanide Antidote)

How it works

It binds cyanide ions to form cyanocobalamin, which is non-toxic and renally excreted, thereby removing cyanide from cytochrome oxidase and restoring cellular aerobic respiration.

Prescribing in practice

• Give promptly in suspected cyanide poisoning without waiting for confirmatory levels, as treatment is time-critical and the antidote has a relatively favourable safety profile.
• It characteristically causes a deep red discoloration of the skin, mucous membranes and urine, and can interfere with several colorimetric laboratory assays.
• Hypertension and hypersensitivity reactions can occur; reconstitute and administer according to the SPC.

Monitoring

Monitor blood pressure, oxygenation and clinical response, and interpret affected laboratory results with awareness of the red discoloration interference.

Counselling the patient

• Team: reddish discoloration of skin and urine is expected and can persist for days.
• Team: some laboratory colorimetric tests may be unreliable after administration.

Evidence & guidelines

High-dose hydroxocobalamin is an established first-line cyanide antidote used in smoke-inhalation and other cyanide-exposure scenarios.