Barbiturate (BARB)

 

CPT Code: 80101
Specimen: Urine
Volume: 30 mL
Container: Use plastic urine drug bottle and evidence tape or tamper-evident container for forensic specimen. Collection kits are available by request from the laboratory.
Collection

Urine specimens should be collected in clean, unbreakable, and leak proof containers.  Freshly voided urine specimens should be used.

Fresh urine specimens do not require any special pretreatment.  No additives or preservatives are required.  Boric acid should not be used as a preservative. 

Specimens may be encountered that display turbidity.  It is recommended that such specimens be centrifuged before analysis.

Specimens should be within the pH range of 5-8.  Specimens with a pH outside this range should be adjusted to this range by the addition of 1N HCl or 1N NaOH before analysis.

Specimens should be at a temperature of 20-25 ⁰C before analysis.

Human urine specimens should be handled and treated as if they are potentially infectious. 

 

Stability: 

 

  If not analyzed immediately, specimens should be stored refrigerated for less than 24 hours. 

  Specimens should be frozen if storage longer than 24 hours is required.

 

 

Cutoff:  200 ng/mL

Note: This method provides only a preliminary analytical test result.  A more specific alternate chemical method must be used in order to obtain a confirmed analytical result.  Gas chromatography/mass spectrometry (GC/MS) is the preferred confirmatory method.  Other chemical confirmation methods are available.  Clinical consideration and professional judgment should be applied to any drug of abuse test result, particularly when preliminary positive results are used.

Use:  Measurements obtained with BARB method are used in the diagnosis and treatment of barbiturates use or overdose.

Information:  Barbiturates, a class of nervous system depressants, are usually taken orally, but are sometimes injected intravenously or intramuscularly.  They are absorbed rapidly; 30-40% is bound to plasma protein, and the rest is distributed to muscle, fat, and to the liver (where they are ultimately inactivated).  They are classified based on their duration of action, ranging from very short acting (approximately 15 minutes) to long acting (a day or more).  Some of the most commonly abused barbiturates are the short-acting ones, including pentobarbital and secobarbital.  An example of a long-acting barbiturate is phenobarbital.  The ratio of unchanged drug to metabolites varies depending upon duration of action.  Short-acting barbiturates will generally be excreted in urine as metabolites, while the long-acting barbiturates will primarily appear unchanged.