Which Antidote is Used in Cyanide Poisoning

Which Antidote is Used in Cyanide Poisoning?

Cyanide poisoning is a life-threatening condition that requires immediate medical intervention. Cyanide is a highly toxic chemical that can be found in various forms, including hydrogen cyanide gas, potassium cyanide, and sodium cyanide. Exposure to cyanide can occur through inhalation, ingestion, or dermal contact, leading to rapid onset of symptoms and potentially fatal outcomes. In this piece, you will explore the antidotes used in the treatment of cyanide poisoning, their mechanisms of action, and the importance of timely medical intervention.

Cyanide Poisoning at a Glance

What is Cyanide?

Cyanide is a potent inhibitor of cellular respiration. It binds to cytochrome c oxidase, an essential enzyme in the mitochondrial electron transport chain, effectively halting ATP production. This process deprives cells of oxygen, leading to cellular asphyxiation and rapid organ failure.

Symptoms of Cyanide Poisoning

The symptoms of cyanide poisoning can appear within seconds to minutes of exposure and include:

  • Headache
  • Dizziness
  • Shortness of breath
  • Nausea and vomiting
  • Rapid heart rate
  • Seizures
  • Loss of consciousness

In severe cases, cyanide poisoning can lead to respiratory arrest, cardiac arrest, and death.

Causes of Cyanide Poisoning

Cyanide poisoning can result from:

  • Inhalation of smoke from fires, especially in enclosed spaces where materials like polyurethane, wool, silk, and synthetic fibers are burning.
  • Industrial exposure in mining, electroplating, and chemical manufacturing.
  • Ingestion of cyanide-containing compounds, such as certain pesticides and rodenticides.
  • Ingestion of cyanogenic plants or seeds, like those from bitter almonds, apricot pits, or certain types of beans.

Antidotes for Cyanide Poisoning

Prompt administration of an appropriate antidote is critical in treating cyanide poisoning. The three main antidotes used are:

  1. Hydroxocobalamin
  2. Sodium Thiosulfate
  3. Sodium Nitrite


Hydroxocobalamin, a form of vitamin B12, is considered one of the most effective antidotes for cyanide poisoning. It works by binding to cyanide ions, forming cyanocobalamin, which is then excreted in the urine. Hydroxocobalamin has several advantages:

  • Rapid onset of action.
  • Direct binding with cyanide, makes it effective even in severe cases.
  • Relatively few side effects.

Mechanism of Action: Hydroxocobalamin combines with cyanide to form cyanocobalamin (vitamin B12), a non-toxic compound that can be safely eliminated by the body.

Dosage and Administration: The standard adult dose is 5 grams administered intravenously over 15 minutes. A second dose may be given if necessary.

Sodium Thiosulfate

Sodium thiosulfate is another antidote used in cyanide poisoning. It acts as a sulfur donor, facilitating the conversion of cyanide to thiocyanate, a less toxic compound that is excreted by the kidneys.

Mechanism of Action: Sodium thiosulfate provides sulfur for the enzymatic conversion of cyanide to thiocyanate, catalyzed by the enzyme rhodanese.

Dosage and Administration: Sodium thiosulfate is often used in conjunction with sodium nitrite. The typical dose is 12.5 grams administered intravenously.

Sodium Nitrite

Sodium nitrite induces methemoglobinemia, which helps to counteract the effects of cyanide. Methemoglobin has a higher affinity for cyanide than cytochrome c oxidase, allowing cyanide to bind to methemoglobin instead, thereby freeing up the cytochrome enzymes and restoring cellular respiration.

Mechanism of Action: Sodium nitrite oxidizes hemoglobin to methemoglobin, which competes with cytochrome c oxidase for binding cyanide, thus reducing the toxicity of cyanide.

Dosage and Administration: The typical adult dose is 300 mg administered intravenously over 2-4 minutes.

Treatment Protocols

Initial Assessment and Stabilization

When cyanide poisoning is suspected, immediate steps should be taken to stabilize the patient:

  1. Remove the Patient from the Source: Ensure the patient is removed from the contaminated area to prevent further exposure.
  2. Administer 100% Oxygen: Provide supplemental oxygen to support cellular respiration and reduce hypoxia.
  3. Monitor Vital Signs: Continuous monitoring of respiratory rate, heart rate, blood pressure, and oxygen saturation is crucial.

Antidote Administration

The choice of antidote depends on the severity of the poisoning and the availability of treatments:

  1. Hydroxocobalamin: Administered as a first-line treatment due to its rapid action and efficacy.
  2. Sodium Thiosulfate and Sodium Nitrite: Often used together in a two-step process. Sodium nitrite is given first to induce methemoglobinemia, followed by sodium thiosulfate to facilitate cyanide detoxification.

Supportive Care

Supportive care includes:

  • Intravenous Fluids: To maintain hydration and blood pressure.
  • Anticonvulsants: To manage seizures if they occur.
  • Cardiopulmonary Support: Mechanical ventilation or advanced cardiac life support may be necessary in severe cases.


Cyanide poisoning is a medical emergency that requires prompt recognition and treatment. Knowing the appropriate antidotes and their mechanisms of action is crucial for effective management. Hydroxocobalamin, sodium thiosulfate, and sodium nitrite are the primary antidotes used, each playing a critical role in detoxifying cyanide and preventing fatal outcomes. Immediate medical intervention and supportive care are essential to improve the chances of recovery. Remember, in cases of suspected cyanide poisoning, seek emergency medical assistance immediately.

By understanding the treatment protocols and the importance of timely antidote administration, we can better prepare to handle such life-threatening situations and save lives.

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