Depending on the type of barbiturate, the drug can stay in your system for just a few days or as long as several weeks.

Barbiturates are a diverse class of medications that were initially used to:

  • Address issues with anxiety
  • Control seizures
  • Induce sedation before surgery
  • Enhance sleep

How do Barbiturates Work?

The exact mechanism of action of many drugs is not fully understood. Barbiturates are believed to work by increasing the efficiency and availability of a neurotransmitter, gamma-Aminobutyric acid (GABA).

When a neuron is activated and releases its neurotransmitter, it releases an entire load of the neurotransmitter it has available; however, it can be modulated to adjust how often it releases its neurotransmitter (how often it fires).

GABA is the major inhibitory neurotransmitter. When it is released, it slows down the firing rates of the neurons in the brain and spinal cord. This is how it exerts its effects and accounts for its medicinal properties.

Not Commonly Prescribed Anymore

Barbiturates were once prescribed regularly to treat anxiety, even anxiety that was not deemed the result of a psychiatric disorder. However, barbiturates became significant drugs of abuse. They have a propensity to produce physical dependence in people who abuse them.

With the development of benzodiazepines, prescription rates for barbiturates have significantly declined. Benzodiazepines were believed to have less abuse potential; although, as it turns out, this is not the case.

Barbiturates may Still be Prescribed:

  • To reduce anxiety before surgery in a hospital or clinic setting
  • As an anesthetic or preanesthetic
  • To older individuals or females to address significant issues with anxiety related to mental health disorders or to address issues with insomnia
  • To control seizures in some individuals (especially phenobarbital)

Younger individuals may be likely to misuse or abuse barbiturates these days. They may get the drug from the medicine cabinets of older relatives who have been prescribed it. Otherwise, the misuse and abuse of barbiturates have significantly declined overall.

The Half-Life of Barbiturates

The half-life of a drug refers to the amount of time it takes your metabolism to reduce the concentration of the drug by half its starting concentration. It is typically used as a measure of how long the drug will remain in your system.

Barbiturates are classified as short-acting, intermediate-acting, and long-acting. The half-lives of barbiturates vary according to the type.

Ultra-Short-Acting Barbiturates

  • Brevital (methohexital): 3–5 hours
  • Pentothal (thiopental): 8–10 hours


  • Seconal (secobarbital): 15–40 hours


  • Amytal (amobarbital): 10–40 hours
  • Butisol (butobarbital): 35–50 hours


  • Mebaral (mephobarbital): 10–70 hours
  • Luminal (phenobarbital): 80–120 hours

How does Half-Life Work?

It is generally considered that it takes between four and five half-lives of a drug for it to be totally eliminated from the body.

If you were to take a drug like Brevital with a half-life of about five hours, the drug should be eliminated from your system within 20 to 25 hours.

Phenobarbital would take much longer. Since it has a variable half-life, it’s best to estimate the length at the end of the half-life range for the drug. If the half-life is 100 hours, it will take between 400 and 500 hours for the drug to be eliminated from your body.

Other Factors That Influence How Long a Drug Remains in Your System

Several Different Factors Can Affect How Long A Barbiturate Will Remain In Your System. These Include:

  • Age and weight
  • Metabolism
  • Physical health
  • Whether or not the barbiturate was taken with other types of drugs or alcohol
  • The type of barbiturate taken

If you take barbiturates with alcohol, there is a good chance that the barbiturate will remain in your system longer than it normally would. Your liver prioritizes metabolizing the alcohol you consumed before metabolizing any other substances.

As you get older, your metabolism slows down. Heavier people will often tend to metabolize drugs a little quicker than those who weigh less. Of course, your physical health and variations in your metabolism will also affect how long your body takes to metabolize any substance.

How Long are Barbiturates Detectable in the Body?

Obviously, this depends on the half-life of the drug and the other factors mentioned above.

Most sources suggest that the majority of barbiturates are detectable in urine for two to four days, but a drug like phenobarbital would be detectable much longer than a shorter-acting drug like Seconal.

In general, shorter-acting barbiturates are detectable in urine for 24 hours, whereas longer-acting barbiturates may be detectable for two to three weeks.

Drugs are often detectable with hair analysis for 90 days or even longer, but this is a very expensive and difficult process. As a result, it is not often used.

They are typically detectable through saliva tests for very short windows of time — for several hours up to one day.

Blood tests may detect the presence of barbiturates for longer periods than saliva tests but typically not as long as urinalysis.


The length of time that any particular barbiturate will be detectable in your system is dependent on several factors, but the main factor is the type of barbiturate you have taken.

Short-acting barbiturates may be detectable in urine for one to four days, whereas long-acting barbiturates may be detectable for several weeks or even longer.

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