What are Barbiturates?

By , BSc

Barbiturates are synthetic drugs used in medicine to depress the central nervous system. The effects range from mild sedation to coma and they may be used a sedatives, hypnotics or as part of anesthesia. Some barbiturates are used to relieve tension or anxiety prior to surgery.

Barbiturates used to be regularly prescribed to treat insomnia, depression and anxiety, but the small difference between a normal dose and an overdose led to a number of accidental deaths, as well as people using them to commit suicide. Therefore, the use of barbiturates as sedatives or hypnotics to relieve insomnia or daytime restlessness caused by everyday stresses is no longer advised and has been replaced with safer medicines.

Today, they are generally only used to treat extreme and serious cases of insomnia. They are also used to help control seizures in epilepsy and some are used as an adjunct to anesthesia.

Pharmacological barbiturates are based on the parent compound barbituric acid. The type of barbituate depends on the substituent used at position 5 of this basic skeleton. Around 2500 different types of barbiturates have been synthesized since 1881, when barbital, the first pharmacologically active form, was synthesized. However only around 50 of these agents have ever been used in medicine.

Availability and Legal Status

Under the Medicines Act, barbiturates are only available as prescription doctors, meaning they can only be bought at a pharmacy with a doctor’s prescription. They are available in the following forms.

  • Tablet
  • Capsule
  • Elixir
  • Solution
  • Suspension
  • Enema
  • Suppository

The Misuse of Drugs Act classes barbiturates as class B drugs, which means they can be bought in accordance with a doctor’s prescription, but any other form of possession or supply counts as an offence. The maximum penalty a person can receive for any unauthorised possession is  5 years in prison and a fine for possession. For supply, the maximum penalty is 14 years in prison and a fine.

If barbiturates are prepared as injection drugs, they are then classified as class A drugs and the penalties for possession and supply are more severe.

Effects of Barbiturates

Barbiturates slow down the CNS in a similar way to alcohol and depending on how rapidly they produce effects and the duration of those effects, they may be classed as ultra-short-, short-, intermediate- or long-acting. In the case of  the long-acting phenobarbital and barbital, effects may last for up to 24 hours and these are used in combination with other drugs to prevent convulsion in epilepsy. The effects of Intermediate-acting barbiturates such as butabarbital sodium last for between 6 and 12 hours and these are used to treat insomnia. Pentobarbital is an example of a short-acting barbituate used to help patients fall asleep. The ultra-short acting thiamylal is administered as an injection to induce unconsciousness patients about to undergo surgery. Gaseous anesthetics are then used to maintain the unconsciousness throughout the surgical procedure.

Small does of barbiturates make people feel relaxed, uninhibited, mildly euphoric, free of anxiety and sleepy.  Larger doses can cause hostility, anxiety, body ataxia, slurred speech, paranoia and suicidal thoughts. The risk of falling over or having an accident is also increased. With prolonged use, tolerance can quickly develop, meaning larger does than the original dose are then required to produce the same effects. This can increase the risk of overdose, signs of which include shallow breathing, rapid and weak pulse, dilated pupils, clammy skin, coma and even death as a result of the central nervous system and respiratory system become severely depressed.


Since tolerance and physical dependence can develop with p prolonged use of barbiturates, withdrawal from regular use can lead to various problems including the following:

  • Irritability
  • Faintness
  • Anxiety
  • Nausea
  • Insomnia
  • Sometimes convulsions

In cases where a person withdraws from regular use of very high doses, symptoms can be more severe and include the following:

  • Low blood pressure
  • Hallucinations
  • Delirium
  • Seizures

Sudden withdrawal from the regular use of high doses can be fatal and for individuals who have become addicted to barbiturates it is essential that they seek the care of trained rehabilitation professionals to help them withdraw safely and effectively.

Further Reading

Last Updated: Jun 19, 2016

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