Specimen Information

Type

Urine, random

Volume

1.0 ml

Transport Info

Refrigerated

Fasting Required?

False

Clinical Significance

Used in the diagnosis and treatment of barbiturate use or overdose.

Barbiturates belong to a broad classification of CNS-Depressant drugs known as sedative-hypnotics. The first barbiturate was barbituric acid, the building block for all subsequent barbiturates, which was produced in 1864 by combining urea with malonic acid. Since then more than 2,500 different barbiturate compounds have been synthesized. Members of the barbiturate family have current medical uses and are prescribed as anticonvulsants, anesthetics, and sedatives and to protect the brain after severe head injury. However, because they readily induce tolerance and dependence and interact detrimentally with many other drugs, especially other CNS depressants, barbiturates are not prescribed as frequently as they once were.When used as an abused substance, barbiturates are usually taken orally in pill form, but habitual users and addicts have been known to dissolve the compounds and inject them hypodermically. Barbiturates are a popular suicide agent in the US. After intake of a high dose, death results from depression of the respiratory and cardiac centers in the brain.Barbiturates are lipid soluble and rapidly absorbed into the bloodstream, readily penetrating the blood-brain barrier. Depending on the degree of lipid solubility, they are commonly characterized as short-, intermediate-, or long-acting. Half lives range from 20 to 120 hours. Barbiturates are variously metabolized by the liver, some being excreted in the urine mainly as active and inactive metabolites and others mainly as unchanged drug. Depending on the specific barbiturate taken, urine may test positive for approximately 30 hours after administration or as long as several weeks.