Cyanides are fast-acting poisons that are lethal and cause painless death. They were used as chemical weapons in World war, and it is found in low levels. It is also found in cigarette smoke, in some food and in-vehicle exhaust, and a bi-product of the human body’s metabolism. 

Cyanide is a chemical that consists of a carbon-nitrogen (CN) bond. The article includes signs and symptoms, diagnosis, Fatal Dose with the fatal period, PM appearances, tests, MLI of Cyanide poisoning.

Deadly forms of Cyanide are:

  • Sodium Cyanide (NaCN)
  • Potassium Cyanide (KCN)
  • Hydrogen Cyanide (HCN)
  • Cyanogen Chloride (CNCl)

The Causes of cyanide poisoning are metallurgy, industrial use, agriculture use, etc.

Signs and Symptoms of Cyanide Poisoning

Symptoms of toxic cyanide poisoning may appear within a few seconds to several minutes after exposure. Common symptoms include:

  • Overall weakness
  • Nausea
  • Confusion
  • Headache
  • Difficulty breathing
  • Seizure
  • Loss of consciousness
  • Cardiac arrest

Effects on the body of cyanide poisoning depend on:

  • Dose
  • Type of Cyanide
  • Period of exposure

Different Ways of Cyanide Poisoning

  1. Acute cyanide poisoning
  2. Chronic cyanide poisoning

Acute Cyanide Poisoning

Acute cyanide poisoning is usually rare, and the majority of cases are from accidental exposure.

Symptoms of Acute Cyanide Poisoning

  • Difficulty breathing
  • Seizure
  • Loss of consciousness
  • Cardiac arrest

Chronic Cyanide Poisoning

Chronic cyanide poisoning can occur if you’re exposed to 20 to 40 ppm over a long period.

Early Symptoms

  • Headache
  • Drowsiness
  • Nausea
  • Vomiting
  • Vertigo
  • Bright red flush

Symptoms After Sometime 

  • Dilated pupils
  • Clammy skin
  • Slower, shallower breaths
  • Weaker, more rapid pulse
  • Convulsions

Without Treatment, the Condition Leads to:

  • Slow, irregular heart rate
  • Reduced body temperature
  • Blue lips, face, and extremities
  • Coma
  • Death

Diagnosis of Cyanide of Poisoning

  • Methemoglobin level- Methemoglobin is considered when there is a concern for smoke inhalation injury.
  • Blood carbon monoxide concentration (carboxyhemoglobin level)- The blood carbon monoxide concentration can indicate how much smoke inhalation has happened.
  • Plasma or blood lactate level- Cyanide blood concentrations usually are not available in time to help diagnose and treat acute cyanide poisoning, but they can later confirm the poisoning.

Fatal Dose with Fatal Period 

  • Fatal immediately with 270 ppm
  • Fatal in 10 minutes with 181 ppm
  • Fatal in 30 minutes with 135 ppm
  • Fatal within half an hour to an hour with 110 to 135 ppm. 

Post-Mortem Appearances of Cyanide Poisoning

External Appearance 

  • The smell of bitter almonds from the body. 
  • Pink patches all over the face, lips, and body.
  • The color of the nails turns blue. 
  • The eyes become brighter with dilated pupils. 

Internal Appearances 

  • The smell of bitter almonds from the stomach and brain. 
  • Severe cavities in the body. 
  • The stomach mucous membranes are pink blood-stained froths that may be found in the trachea and bronchi.
  • When potassium Cyanide has been taken, observe the slight corrosion in the mouth, redding the mucous membrane (brick red to brown).

Tests of Cyanide Poisoning

There are several tests for testing the presence of Cyanide. It includes odor tests and color tests.

The Odour Test

  • The peculiar smell of Cyanide is of bitter almond.

The Color Test

  1. The Prussian Blue Test: The solution containing Cyanide is made with caustic potash + 0.5ml of freshly prepared ferrous sulfate solution + a few drops of ferric chloride solution + warm with dilute sulfuric acid. Blue color or blue precipitate indicates the presence of Cyanide.

2. The Sulfonamide Test: The alkaline solution containing Cyanide + few drops of yellow ammonium sulfide + evaporated to dryness in the hot water bath. The formation of the residue is dissolved in a few drops of diluted hydrochloric acid and gives blood red. Blood red color with one drop of ferric chloride solution indicates the presence of Cyanide. 

Medico-Legal Importance 

Homicidal Death

  • Homicidal deaths are caused to others by the person like killing or commission of murder etc. 
  • Cyanide is the best weapon for causing a homicidal type of death, but it is rarely used. 
  • It has been used legally to kill convicted criminals in some of the states of the USA.
  • Cyanide is rarely used for homicidal poisoning because of its unique smell and taste. 

Suicidal Death 

Cyanide is very popular for suicidal deaths because it causes quick or instant death. 

Accidental Deaths

  • Accidental deaths are those types of deaths that are caused by some mistake or some misunderstanding. 
  • In the case of Cyanide, accidental exposure to Cyanide may happen when the workers in industries handle Cyanide during their occupations. 
  • Several laws deal with poison, and poisonous substances like, Poison Act, 1919, The Poison And Dangerous Substances Act, 1957, etc.


Cyanide or CN is an inorganic poison which is found in solid, liquid and gaseous state. These poisons are available on the earth, causing a painless and quick death. 

When the Cyanide enters the blood cell, it prevents the cell from reacting with oxygen, and then due to lack of oxygen reactions in the body, death takes place. 

The commonly available Cyanide exists in powdered form of white color. It causes various effects on the body after consuming Cyanide, and the major effect is the bitter almond effect. 

Categories: Toxicology


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