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What is Barbiturates (BAR) Blood test? 

Barbiturates are a group of sedative medicines that were used to treat certain disorders of the nervous system such as insomnia and anxiety. The problem with barbiturates, however, is that they have several side effects and may lead to drug dependence. Thus, they have largely been replaced by another group of drugs called the benzodiazepines. Despite the risks, some of the barbiturates are still prescribed by doctors as an anaesthetic and for the management of recurrent fits, also known as epilepsy. They are also abused as a recreational drug. 

BAR blood test is a screening test that is performed to check for the presence of barbiturates in the blood sample of a person. It is mainly done to look for drug abuse or drug toxicity.

  1. Why is BAR (Barbiturates) Blood test performed?
  2. How do you prepare for BAR (Barbiturates) Blood test?
  3. How is a BAR (Barbiturates) Blood test performed?
  4. What do BAR (Barbiturates) Blood test results mean?

The test is usually ordered for employment or legal purposes to detect the presence of barbiturates in a person’s blood sample. The following list describes the instances where a doctor may order this test:

  • Random workplace testing
  • Post-accident testing
  • Return-to-duty testing
  • Follow-up testing in case of ongoing treatment
  • Pre-employment testing

If a person has been brought unconscious to the hospital and shows signs of drug toxicity, the doctor may order this test to check for barbiturate use. Barbiturates can be detected in blood in as early as 15-60 minutes after ingestion and are detectable for up to 52 hours in most cases. 

BAR blood test may also be done as a part of drug screening if a patient shows symptoms of drug abuse such as:

You do not require any special preparation before this test. Make sure to tell the doctor if you are taking any medicines. This includes prescription and non-prescription medicines, illegal drugs, herbs and supplements. This is because some supplements and medicines may interfere with the test results.

A doctor or technician will withdraw seven to 10 mL of blood from a vein in your arm. You may feel a piercing pain when the needle is inserted, but it will subside soon as the needle is removed. A small amount of bruising around the area of blood withdrawal is normal. However, if the bruising does not fade away after some time, please consult your doctor.

Normal results:

A normal result is generally reported as negative in the BAR blood test. It means that either no traces of barbiturate were found in your blood sample or the amount detected was below the cut-off value. A cut-off is a predetermined threshold value for the body levels of a drug. It may vary from one laboratory to the other and on the type of barbiturate being checked.

The following is a list of cut-off values for some barbiturates, in nanograms/millilitre (ng/mL):

  • Butalbital: 60 ng/mL 
  • Amobarbital: 60 ng/mL
  • Pentobarbital: 100 ng/mL
  • Secobarbital: 100 ng/mL
  • Phenobarbital: 60 ng/mL

Some places may report values in different units. For example, a therapeutic concentration of 2-30 mg/L (milligrams per litre) of phenobarbital is considered normal.

Abnormal results:

An abnormal result in the BAR blood test is usually reported as positive. This implies that the blood sample you gave had barbiturates beyond the cut-off value. Depending on the amount detected, your doctor can infer if it is due to drug intake or toxicity. For example, toxic effects have been seen with 4-90 mg/L of phenobarbital and values of 4-120 mg/L have been associated with fatalities.

An abnormal result, however, does not always mean drug usage. False-positive results can occur due to cold and cough medicines, antibiotic therapy and ibuprofen intake. Talk to your doctor to get the correct interpretation of the result.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

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References

  1. European Monitoring Centre for Drugs and Drug Addiction [Internet]. European Union. Lisbon. Portugal. Europe. Barbiturates drug profile
  2. National Institute of Drug Abuse. National Institute of Health [internet]. U.K. Drug Testing
  3. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Drug Testing
  4. Wilson D ,Manual of Laboratory and Diagnostic Tests, 2008. The Mc Graw Hills companies Inc., Pp: 560.
  5. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests
  6. Winterhack, Flanagan. Marshfield Labs: Marshfield Clinic [internet]. Wisconsin. U.S.A., Current Cutoff Levels for Toxicology Tests