How Long Does Phenobarbital Stay in Your System?

Detection Timetable Depends on Many Variables

Phenobarbitol tablets
Phenobarbital Is a Barbiturate. DEA

How long phenobarbital is detectable in the body depends on many variables, including which kind drug test is being used. Phenobarbital - which is a barbiturate - can be detected for a shorter time with some tests, but can be "visible" for up to three months in other tests.

The timetable for detecting phenobarbital in the system is also dependent upon each individual's metabolism, body mass, age, hydration level, physical activity, health conditions and other factors, making it almost impossible to determine an exact time phenobarbital will show up on a drug test.

The following is an estimated range of times, or detection windows, during which phenobarbital can be detected by various testing methods:

How Long Does Phenobarbital Stay in Urine?

Phenobarbital can be detected in a urine test for up to 2-3 weeks

How Long Does Phenobarbital Remain in the Blood?

Blood tests for Phenobarbital can detect the drugs for up to 5-10 days

How Long Can Phenobarbital Be Detected in Saliva?

A saliva test can detect Phenobarbital for 1-10 days

How Long Does Phenobarbital Remain in Hair?

Phenobarbital, like many other drugs, can be detected with a hair follicle drug test for up to 90 days.

Take Phenobarbital Only as Prescribed

Phenobarbital is usually prescribed to control seizures, in some circumstances it is used in treating withdrawal and for other purposes. Given its narrow therapeutic window and potential for abuse, it is no longer generally prescribed for anxiety or sleep.

One reason to know how long phenobarbital remains in your system is because it is addictive. Taking larger doses, taking it more often, or taking it longer than prescribed could increase the risk of addiction.

Because phenobarbital can become habit-forming, you should not take the medication if you drink or have ever drunk large amounts of alcohol, used illicit drugs, or overused or used for nonmedical purposes any prescription medications.

Don't Stop Taking Phenobarbital Suddenly

Also, do not stop taking phenobarbital suddenly without consulting your healthcare provider. Stopping suddenly can cause you to experience withdrawal symptoms which can include:

If you wish to stop taking phenobarbital, your doctor will probably gradually decrease your dosage.

Preventing a Phenobarbital Overdose

Phenobarbital is in a class of medications called barbiturates. It works by slowing activity in the brain and can cause relaxation and sleepiness. Phenobarbital is prescribed to control seizures.

To prevent an overdose, do not take larger doses, take it more often, or take it for a longer time than prescribed by your healthcare provider. Barbiturates are also highly addictive and should be taken only as directed.

Symptoms of Phenobarbital overdose can include:

  • Uncontrollable movements of the eyes

If you think someone has had a Phenobarbital overdose, call the poison control center at 1-800-222-1222. If the person has collapsed or is not breathing, call 9-1-1 immediately.


Always Test Clean. "What Are Drug Detection Times?" Drug Test Facts Accessed December 2015

American Association for Clinical Chemistry "Drugs of Abuse Testing." Lab Tests Online. Revised 2 January 2013.

LabCorp, Inc. "Drugs of Abuse Reference Guide." Accessed March 2013.

OHS Health & Safety Services. "How long do drugs stay in your system?." Accessed March 2013.

National Institue on Drug Abuse. "Phenobarbital." Drugs, Herbs and Supplements May 2015

Continue Reading