Benzodiazepines are generally classified as minor tranquilizers useful in the management of anxiety. Benzodiazepines include drugs such as diazepam (Valium®), chlordiazepoxide (Librium®), oxazepam (Serax®), lorazepam (Ativan®), alprazolam (Xanax®), clonazepam (Clonopin®), and others. Some, such as flurazepam (Dalmane®), alprazolam (Xanax®) and triazolam (Halcion®), are used as sleeping aids. They have generally replaced barbiturates in the induction of sleep and sedation. Clonazepam (Clonopin®) is useful in the treatment of epilepsy. Many common benzodiazepines are detected in urine by their metabolites oxazepam and nordiazepam. Benzodiazepines are prescription drugs and occasionally sold on the illicit market. They are widely prescribed and relatively free of dangerous acute toxic overdose effects. Some illicit fake methaqualone (Quaalude) from Mexico actually contains large doses of diazepam.
Benzodiazepines have varied effects and as many as 2,000 have been synthesized. They act selectively on the polysynaptic pathways throughout the central nervous system. Benzodiazepine receptor sites have been identified in the brain. The mechanism of action may be related to the metabolism of gamma aminobutyric acid (GABA). Benzodiazepines undergo extensive biotransformation (metabolism) and identification of the particular benzodiazepine is best performed on blood following a positive urine screening.
The immunoassays (EIA) are utilized to detect benzodiazepines in urine. All positives are confirmed by GC/MS.
Cutoff and Detection Post Dose
Cutoff by immunoassay is 200 ng/ml for benzodiazepine metabolites. This level is sufficient to detect the most common benzodiazepines for 48-72 hours post single dose and as long as a week post dose under some circumstances. GC/MS cutoff levels for the various benzodiazepine metabolites is 100 ng/ml.