Barbiturates: Uses, Fatal Dose, Poisoning Symptoms, Metabolism, Medico-Legal Importance

Barbiturates: Uses, Fatal Dose, Poisoning Symptoms, Metabolism, Medico-Legal Importance

Barbiturate is one of the important sedatives or analgesics drugs that are tremendously being used as drugs of addiction. These have depressant effects upon the body and make it insensitive to pain or depression.

All barbiturates are derivatives of barbituric acid. The variations are found due to the substitution of hydrogen atoms by alkyl, aryl, or other groups. They are also known as barbitones or barbitals. These substances are increasingly being used by drug addicts as they are comparatively more easily available, less costly, and are considered less dangerous. 

Classification of Babiturates Based on Time of Action

  • Long-Acting Barbiturates– These drugs induce sleep from 8 to 24 hours are long- acting. An example includes Barbitone, Pheno-barbitone, Methyl Phenobarbitone etc. 
  • Intermediate Acting Barbiturates– These drugs produce effect in less duration from 4 to 10 hours are intermediate- acting. An example includes Allobarbitore, Butobarbitone and Amylobarbitone
  • Short-Acting Barbiturates– These drugs produce effect upto 3 to 4 hours are short- acting. An example includes Cyclobarbitone and pentobarbitone
  • Ultra Short Acting Barbiturate– These drugs are used as rapidly acting anaesthetics are ultra-short acting. Its examples include Methohexital, Thiomylal, Thiopental, etc.

Uses of Barbiturates

They have acquired tremendous importance in recent years. They are extensively used in medicine as hypnotics to induce sleep and relieve pain in case of a nervous breakdown, emotional upsets. It has also been used as a ‘truth serum’. By administration, a state of semi-consciousness is produced in the subjects. This state is conductive to get truthful answers from the subject hence the name ‘truth serum’.

Administration of Barbiturates

Barbiturates are frequently administered orally. However, they are sometimes administered using injection too. If taken in excess produce intoxication often with severe withdrawal syndromes. They are sometimes taken by opiate addicts as substitutes. Likewise, alcoholics also sometimes substitute them for liquor.

The intoxication caused by barbiturates may not be so obvious as they have no smell. For example- emotional tension developed by cocaine or amphetamine addicts may be controlled. Likewise, the intoxication of alcohol may be prolonged if the same is taken along with barbiturates.

Fatal Dose of Barbiturates

Fatal dose is comparatively large though it varies with the compound. For example-

  • For Short-acting Barbiturates –> 1 to 2 g. 
  • For Medium-acting Barbiturates –> 2 to 3 g. 
  • For Long-acting Barbiturates –> 3 to 5 g. 
  • For Ultra short Barbiturates –> 6-10 gm

The fatal period of these substances is One to two days.

Sign and Symptoms of Barbiturate Poisoning 

If they are taken in excess amount leads to several problems in the body and also affects the human body in different ways. However, the effect varies with individuals. Some reported Signs and symptoms of barbiturates are mentioned below-

For Acute Poisoning symptoms include-

  • Drowsiness 
  • A short period of confusion
  • Excitement
  • Delirium
  • Hallucinations 
  • Ataxia
  • Vertigo
  • slurred speech
  • Headache
  • Paraesthesias

For Chronic Poisoning, symptoms are as follows-

  • Poor judgement
  • Loss of memory
  • Skin eruption (cutaneous bullae)
  • Constipation
  • Irritability
  • Ataxic gait
  • Stammering
  • Cramps and orthostatic hypotension. 

Withdrawal syndrome of barbiturate addiction includes anxiety, twitching of muscles, tremors in hands and fingers, weakness, giddiness, nausea, vomiting, insomnia, lowering of blood pressure, and delirium.  

Metabolism of Barbiturates

Barbiturates metabolize in 4 ways i.e.,

  • The aryl or alkyl substituent gets oxidized.
  • N-alkyl group is dealkylated.
  • Fission of ring takes place but only to small extent.
  • Thiobarbiturates lose sulphur.

Treatment of Barbiturates

There are multiple methods for treating individuals addicted to barbiturates. Here are some of the effective treatments given below for Barbiturate poisoning- 

  • Gastric lavage is administered with warm water mixed with potassium permanganate.
  • Suspension of activated charcoal is very effective.
  • Artificial respiration and oxygen is given.
  • Normal saline with 5% glucose should be given in 24 hours. 
  • Bowels should be evacuated by enema. 
  • Charcoal haemoperfusion. 
  • Peritoneal dialysis is also given.

Medico-legal Importance of Barbiturates

  • Many cases of suicide are reported by using short-acting barbiturates. 
  • Thiopental is used as truth serum to extract the truth from the criminals during interrogation by inducing a state of hypnosis in Narcoanalysis process. 
  • Accidental poisoning and Homicidal poisoning cases are also reported.

Identification of Drug

On the reported barbiturate drug cases, Dilli – Koppanyi test was mostly preferred in the forensic laboratories.

In this test, barbiturates produce blue colour with 1% solution of cobalt nitrate in alcohol and a pellet of sodium hydroxide. Forensic toxicological analysis of Stomach contents, Urine, blood, Kidney, Brain and Liver is done. Many more instrumentation methods are reliable for testing these substances which includes Thin Layer Chromatography, UV and IR Spectrophotometry, Gas chromatography and High Pressure Liquid Chromatography.


Drug addiction to barbiturate is characterized by a strong desire to continue taking the drug, a tendency to increase the dose as well as physical and psychological dependence.

Barbiturate in small doses cause sleep but in larger doses they cause insomnia. An addict gets intoxicated even with a small dose because of the cumulative effects.

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