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Antidotes & Toxicology Pregnancy: No data in pregnancy; cyanide poisoning is a medical emergency that can be fatal to the woman and fetus - life-sustaining therapy should not be withheld. Recommended (with sodium thiosulfate) if cyanide poisoning is known or suspected.

Sodium Nitrite

Brand names: Sodium Nitrite Injection

Sodium nitrite is an intravenous antidote used, often with sodium thiosulfate, in the emergency treatment of acute cyanide poisoning.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 10 mL (300 mg) IV
Route: Intravenous (slow IV injection)
Frequency: Single dose at 2.5-5 mL/minute, given first and immediately followed by sodium thiosulfate 50 mL
Max: 10 mL (300 mg) - one vial (30 mg/mL)
For acute life-threatening cyanide poisoning, adjunctive to airway, ventilatory and circulatory support. Give sodium nitrite first, then immediately sodium thiosulfate 50 mL. Blood pressure must be monitored during infusion; decrease the rate if significant hypotension occurs. Redosing: if signs of poisoning reappear, repeat treatment using one-half the original dose of both sodium nitrite and sodium thiosulfate. In known anaemia, reduce the sodium nitrite dose proportionately to the haemoglobin concentration. Chemically incompatible with hydroxocobalamin - do not administer via the same IV line. One vial (300 mg/10 mL) constitutes a single dose.

Paediatric dose

Dose: 6 mg/kg
Route: Intravenous (slow IV injection)
Frequency: Single dose at 2.5-5 mL/minute, immediately followed by sodium thiosulfate
Max: 10 mL (300 mg)
Children: 0.2 mL/kg (6 mg/kg or 6-8 mL/m2 BSA) not to exceed 10 mL. Use with caution in patients less than 6 months of age (higher risk of severe methaemoglobinaemia). Reduce proportionately in known anaemia. Verify against a children's formulary.

Dose adjustments

Renal

Substantially excreted by the kidney; risk of adverse reactions may be greater in renal impairment - care in dose selection and monitor renal function.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Children: 0.2 mL/kg (6 mg/kg or 6-8 mL/m2 BSA) not to exceed 10 mL. Use with caution in patients less than 6 months of age (higher risk of severe methaemoglobinaemia). Reduce proportionately in known anaemia. Verify against a children's formulary.

Verify in a children's formulary

Contraindications

  • None stated (US label lists 'None')

Side effects

  • Syncope, hypotension, tachycardia, palpitations, dysrhythmia
  • Methaemoglobinaemia
  • Headache, dizziness, blurred vision, seizures, confusion, coma
  • Nausea, vomiting, abdominal pain
  • Tachypnoea, dyspnoea

Interactions

  • Formal drug interaction studies have not been conducted
  • Chemically incompatible with hydroxocobalamin - do not give in the same IV line

Clinical monograph

How it works

It oxidises haemoglobin to methaemoglobin, which preferentially binds free cyanide as cyanmethaemoglobin, drawing cyanide away from cytochrome oxidase and restoring cellular aerobic respiration.

Prescribing in practice

  • It deliberately induces methaemoglobinaemia, so it can cause dangerous hypoxia and hypotension and must be given cautiously, particularly where smoke inhalation may coexist with carbon monoxide poisoning.
  • Administer by slow intravenous injection with close haemodynamic monitoring because of its vasodilator and hypotensive effects.
  • Treatment of serious cyanide poisoning should follow specialist toxicology or poisons-centre advice, and an alternative antidote may be preferred in some situations.

Monitoring

Monitor blood pressure continuously and check methaemoglobin levels to avoid excessive methaemoglobinaemia during and after treatment.

Counselling the patient

  • Explain to the team that this antidote works by creating a controlled level of methaemoglobin to trap cyanide.
  • Highlight the need to watch closely for a fall in blood pressure during administration.
  • Note that it is typically used alongside a second agent such as sodium thiosulfate.

Evidence & guidelines

Sodium nitrite combined with sodium thiosulfate is a long-established regimen for acute cyanide poisoning, with use guided by UK poisons information (TOXBASE) advice.

Reference: NPIS Toxbase; Poisoning Emergency Book; WHO Model Formulary; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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Sodium Nitrite is a core drug in the following exam-focused workups on our sister siteReviseMRCEM.

MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.