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Hydroxocobalamin

AEMPS

Vitamin B12 (European form of choice) and cyanide poisoning antidote

ATC code: B03BA03

Brand names: Cyanokit, Hydroxocobalamin

Updated · Methodology

Indications

A

Cyanide poisoning

First line

Hydroxocobalamin as Cyanokit (SERB) is the first-line antidote for cyanide poisoning, including smoke inhalation from polymer fires. AEMPS registers Cyanokit 5 g IV. Dose: 5 g IV over 15 minutes (up to 10 g in severe poisoning). Advantage over nitrite plus sodium thiosulfate: no methaemoglobinaemia or hypotension, so safe with concurrent carbon monoxide poisoning. Colours skin, mucosa and urine red or pink for 1–7 days – not concerning, but distorts lab tests (bilirubin, creatinine, magnesium).

Sources

  1. AEMPS: Ficha técnica de Cyanokit (hidroxocobalamina) (2023)
  2. Emerg Med Australas: Review article: management of cyanide poisoning. (2012)
  3. Eur J Emerg Med: Cyanide poisoning by fire smoke inhalation: a European expert consensus. (2013)
  4. Pediatr Emerg Care: Pediatric cyanide poisoning by fire smoke inhalation: a European expert consensus. Toxicology Surveillance System of the Intoxications Working Group of the Spanish Society of Paediatric Emergencies. (2013)

ICD-10: T57.3 · ICD-11: NE61

A

Vitamin B12 (cobalamin) deficiency

First line

Hydroxocobalamin is the European form of choice for treating confirmed vitamin B12 deficiency in patients with pernicious anaemia, after gastric or ileal resection, and in vegetarians and vegans with confirmed deficiency. 2024 and 2014 recommend induction 1000 μg IM three times weekly for 2 weeks then maintenance 1000 μg every 2–3 months for life. Advantage over cyanocobalamin: fewer injections due to longer half-life. With neurological symptoms (subacute combined degeneration), induction may be extended until neurological recovery or plateau.

Sources

  1. AEMPS: Ficha técnica de Megamilbedoce (hidroxocobalamina) (2022)
  2. NICE: Vitamin B12 deficiency in over 16s: diagnosis and management (NG239) (2024)
  3. BSH: Guidelines for the diagnosis and treatment of cobalamin and folate disorders (2014)

ICD-10: E53.8 · ICD-11: 5B5F

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

D

Anti-aging and longevity

Not recommended

Hydroxocobalamin is a form of vitamin B12 used to treat B12 deficiency and the anemia linked to it. Marketers promote it for anti-aging and longevity as a way to "rejuvenate" and slow aging, but no convincing benefit has been shown for that use – there is no solid evidence that taking it for longevity helps people whose B12 levels are normal. When B12 is already adequate, extra doses do not produce an anti-aging effect. What actually affects aging is sleep, diet, physical activity, not smoking, and keeping blood pressure and blood sugar in check; B12 is worth supplementing only when lab tests confirm a deficiency.

Sources

  1. Cochrane: Vitamin D supplementation for prevention of mortality in adults (2014)
  2. NICE: Vitamin B12 deficiency in over 16s: diagnosis and management (NG239) (2024)
How to read tiers A–F
  • AStrong evidence – first or second line in international guidelines
  • BRecommended in selected cases
  • CStudy data contradict each other
  • DBenefit not proven, no documented harm
  • FDocumented harm, or risk without benefit

Mechanism of action

Hydroxocobalamin is converted to active B12 forms (methylcobalamin and adenosylcobalamin) and serves as cofactor for methionine synthase and L-methylmalonyl-CoA mutase. Long plasma half-life (~26–31 days) gives an advantage over cyanocobalamin: fewer maintenance injections. In cyanide poisoning hydroxocobalamin binds the cyanide ion into non-toxic cyanocobalamin excreted by the kidneys. Dose 5 g IV over 15 minutes is the antidote standard (Cyanokit).

Safety

Contraindications

  • Hypersensitivity to hydroxocobalamin
  • Leber hereditary optic neuropathy

Serious adverse effects

  • Anaphylactic reactions (rare)
  • Acute kidney injury with urinary oxalate crystals (reported after high-dose Cyanokit)
  • Lab test interference for 1–2 weeks (bilirubin, creatinine, magnesium, total protein, ALT)

Common adverse effects

  • Reddish-pink discolouration of skin, mucosa and urine (1–7 days after Cyanokit)
  • Acneiform rash
  • Nausea
  • Transient hypertension with rapid IV administration
  • Headache

Pregnancy: can you take Hydroxocobalamin?

AEMPS summary of product characteristics (section 4.6): in pregnancy, hydroxocobalamin is not used to treat megaloblastic anaemia unless vitamin B12 deficiency has been demonstrated. The section gives no other information on pregnancy, including risk to the fetus.

Breastfeeding: can you take Hydroxocobalamin?

Compatible (Hale L1) at physiological doses. After a 5 g antidote dose, milk concentration is markedly elevated; AEMPS recommends interrupting breastfeeding for 7–14 days with expression and disposal.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Label mentions2 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

  • anticonceptivos hormonalesclass named in the label
    «Los pacientes tratados con cloranfenicol pueden responder débilmente a Hidroxocobalamina Basi. Las concentraciones séricas de hidroxocobalamina pueden verse disminuidas por anticonceptivos orales…»

    AEMPS, section 4.5 · Open on CIMA

  • Chloramphenicol
    «Los pacientes tratados con cloranfenicol pueden responder débilmente a Hidroxocobalamina Basi. Las concentraciones séricas de hidroxocobalamina pueden verse disminuidas por anticonceptivos orales…»

    AEMPS, section 4.5 · Open on CIMA

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Frequently asked

What is Hydroxocobalamin used for?

Hydroxocobalamin is evaluated for the following indications with varying evidence strength: Vitamin B12 (cobalamin) deficiency (evidence tier A), Cyanide poisoning (evidence tier A), Anti-aging and longevity (evidence tier D). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Hydroxocobalamin?

Common side effects of Hydroxocobalamin (≥ 1 in 100): Reddish-pink discolouration of skin, mucosa and urine (1–7 days after Cyanokit), Acneiform rash, Nausea, Transient hypertension with rapid IV administration, Headache. See the Safety section for uncommon and serious reactions.

Is Hydroxocobalamin safe during pregnancy?

AEMPS summary of product characteristics (section 4.6): in pregnancy, hydroxocobalamin is not used to treat megaloblastic anaemia unless vitamin B12 deficiency has been demonstrated. The section gives no other information on pregnancy, including risk to the fetus.

Is Hydroxocobalamin compatible with breastfeeding?

Compatible (Hale L1) at physiological doses. After a 5 g antidote dose, milk concentration is markedly elevated; AEMPS recommends interrupting breastfeeding for 7–14 days with expression and disposal.

Who should not take Hydroxocobalamin?

Hydroxocobalamin is contraindicated in: Hypersensitivity to hydroxocobalamin; Leber hereditary optic neuropathy. Full list in the Safety section.

Official sources

Direct links to regulator labels. Open in a new tab.

Other drugs in this group

Cyanocobalamin, Folic acid, Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin), Methylcobalamin, Levomefolate (L-methylfolate, 5-MTHF), Vitamin B12 (cobalamin)