Barbituates, Urine Screen UDRG4

• Urine specimens may be collected in plastic (i.e., polypropylene, polycarbonate, polyethylene) or glass containers. Some plastics, other than those listed, can adsorb certain drugs.
• If not analyzed immediately, specimens may be stored at room temperature at 15 - 25^o C for up to 7 days following collection. After 7 days, specimens should be stored frozen at <= -20^o C. Frozen specimens must be completely thawed and mixed thoroughly prior to analysis.
• Specimens with high turbidity should be centrifuged before analysis. The recommended pH range for urine specimens is 3.0 - 11.0. Adulteration of the urine specimen may cause erroneous results. If adulteration is suspected, obtain another specimen. Human urine specimens should be handled and treated as if they are potentially infectious.

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 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.

The Emit II Plus Barbiturate Assay tests for both long- and short-acting barbiturates in human urine. Positive results for samples containing other compounds structurally unrelated to barbiturates have not been observed. The cutoff level for distinguishing positive from negative samples is 200 ng/mL.

Analytical Principle:  The Emit II Plus Barbiturate Assay is a homogeneous enzyme immunoassay technique used for the analysis of specific compounds in human urine.

The Emit II Plus Barbiturate Assay provides only a preliminary analytical test result. A more specific alternative chemical method must be used to obtain a confirmed analytical result. Gas chromatography/mass spectrometry (GC/MS) is the preferred confirmatory method but 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.