Cyanide Poisoning

What to do now

1. Protect yourself first. Do not enter a smoke-filled or chemical-contaminated area without protective equipment. Rescuers can become victims.
2. Call 911 or your local emergency number. Say that cyanide or smoke exposure is possible.
3. Move the person to fresh air if you can do so safely.
4. Remove contaminated clothing and seal it in a plastic bag. Wash skin with plenty of soap and water if liquid cyanide touched it. Flush eyes with water for 10 to 15 minutes.
5. If the person is not breathing normally, start CPR with chest compressions. Avoid mouth-to-mouth if the person swallowed cyanide or it is on their face; use a barrier device if available.
6. Do not induce vomiting.
7. For mild exposures or questions, call Poison Help at 1-800-222-1222 in the US, available 24/7.

How cyanide affects the body

Cyanide binds to an enzyme in mitochondria (cytochrome c oxidase) that cells need to use oxygen to make energy. Cells switch to an inefficient backup process that produces lactic acid. Organs that need the most oxygen, the brain and heart, fail first. Blood still carries plenty of oxygen, so the skin may look pink or flushed rather than blue, and pulse oximeter readings can look normal.

Sources of cyanide

• House and building fires: burning plastics, polyurethane foam, nylon, wool, silk and insulation release hydrogen cyanide. Many fire victims have both cyanide and carbon monoxide poisoning, and the two together are especially dangerous. See smoke inhalation.
• Industry: electroplating, metal cleaning, mining (gold extraction), photography, plastics manufacturing and chemical laboratories.
• Plants and foods: apricot, peach and cherry kernels, bitter almonds, and cassava that has not been properly soaked and cooked contain compounds that release cyanide when eaten.
• Medicines: prolonged high-dose infusion of sodium nitroprusside, a blood pressure medicine used in hospital.
• Some pesticides and rodenticides, and deliberate poisoning.
• Supplements: amygdalin (laetrile or "vitamin B17"), promoted as a cancer treatment, can cause cyanide poisoning and is not an approved or effective treatment.

Symptoms

Symptoms depend on the dose, route and duration. Inhaled cyanide acts within seconds to minutes; swallowed cyanide salts within minutes; plant sources over hours.

Early or mild

• Headache, dizziness and confusion
• Anxiety and restlessness
• Fast breathing and breathlessness
• Nausea and vomiting
• Fast heart rate
• Eye and throat irritation

Severe

• Seizures
• Loss of consciousness and coma
• Slow heart rate and low blood pressure
• Breathing that slows and stops (respiratory failure)
• Cardiac arrest

A "bitter almond" smell on the breath is described, but many people cannot smell it, so it is not reliable.

Diagnosis

Cyanide poisoning is diagnosed mainly from the situation and symptoms, because blood cyanide levels take too long to return. Treatment starts before confirmation. Supporting signs include:

• very high blood lactate (often above 8 mmol/L in fire victims), indicating lactic acidosis
• severe metabolic acidosis
• unusually high oxygen levels in venous blood, because tissues are not using it
• carbon monoxide levels, measured at the same time in fire victims

Treatment

Supportive care

• 100% oxygen by mask or breathing tube
• Breathing support and ventilation if needed
• IV fluids and medicines to support blood pressure
• Seizure control
• Correction of acidosis

Antidotes

• Hydroxocobalamin (Cyanokit): the preferred antidote, especially in fire victims. It binds cyanide to form cyanocobalamin (vitamin B12), which the kidneys excrete. It turns the skin and urine red for days, which is harmless, but can interfere with some lab tests.
• Sodium nitrite and sodium thiosulfate: an older antidote combination. Sodium nitrite is avoided in fire victims because it reduces the blood's oxygen-carrying capacity, worsening carbon monoxide poisoning.

Antidotes are given by trained medical staff based on symptoms, without waiting for test results.

Complications and outlook

People who receive prompt treatment, and those with mild exposures, often recover fully. Severe poisoning can cause brain damage, including movement disorders similar to Parkinson's disease, memory problems and personality changes. Death can occur within minutes of a high inhaled dose.

Prevention

• Install smoke alarms and plan fire escape routes. Never re-enter a burning building.
• Follow workplace safety rules, ventilation and protective equipment requirements when handling cyanide compounds.
• Do not eat apricot kernels or bitter almonds in quantity, and do not take amygdalin supplements.
• Soak, ferment and cook cassava thoroughly before eating.
• Store chemicals securely and out of reach of children.

Frequently asked questions

What are the symptoms of cyanide poisoning?

Early symptoms include headache, dizziness, confusion, fast breathing, nausea and anxiety. Severe poisoning causes seizures, collapse, slow heart rate, breathing failure and cardiac arrest, sometimes within minutes of inhaling cyanide gas.

What is the most common source of cyanide poisoning?

In developed countries, smoke from house and building fires is the most common source, as burning plastics, foam and fabrics release hydrogen cyanide. Industrial accidents, certain plant foods and deliberate poisoning are less common sources.

What is the antidote for cyanide poisoning?

Hydroxocobalamin, sold as Cyanokit, is the preferred antidote. It binds cyanide to form vitamin B12, which leaves the body in urine. An older combination of sodium nitrite and sodium thiosulfate is also used, but not usually in fire victims.

Can you survive cyanide poisoning?

Yes. Many people survive with fast removal from exposure, oxygen and antidote treatment. Survival depends on the dose and how quickly treatment starts. Some survivors of severe poisoning have lasting brain effects.

Are apricot kernels poisonous?

They can be. Apricot kernels contain amygdalin, which releases cyanide in the body. Eating several raw kernels can cause poisoning, especially in children. Health authorities advise against eating them or taking amygdalin supplements.