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Sedatives-Barbiturates-Hypnotics Screen, plasma or serum

Alternate test name

Lab area
Clinical Biochemistry - TDM & Toxicology
Method and equipment
Expected turn-around time
Stat: 3 hours Routine: 24 hours
Specimen type

Serum, Plasma (Heparin, Citrate or EDTA)

Specimen requirements

1.0 mL

Storage and transportation

4° C (transport with a cool pack if possible). Dry ice if frozen.

Stability information:

Refrigerated 7 days

Frozen > 7 days

Background and clinical significance

The Barbiturates are a large group of structurally similar sedative-hypnotic drugs which are subject to abuse. Screening assays such as this are used to establish the presence or absence of the drug class based on a pre-determined threshold value. Alternative methods must be employed to determine the identity and concentration of any barbiturate from a positive screening result. Barbiturates are grouped into short-acting and long-acting as follows:

  • Ultra-short acting: Thiopental
  • Short acting: Pentobarbital, Secobarbital
  • Intermediate acting: Amobarbital, Butabarbital, Butalbital 
  • Long acting: Phenobarbital, Barbital

The Sedative-hypnotics are a large group of drugs which cause CNS depression. Most stimulate the activity of Gamma Aminobutyrate (GABA), the principle inhibitory neurotransmitter in the CNS. 

  • Barbiturates: Meprobamate, Methaqualone

Many of the symptoms seen with barbiturate toxicity are also observed with the sedative-hypnotics. These include: lethargy, coma, hypothermia, slurred speech, irritability, respiratory depression and cardiovascular complications.

Pentobarbital is an short acting barbiturate which depresses the central nervous system and induces hypnosis and anesthesia.  Recovery after a dose is rapid with some slow somnolence and antergrade amnesia.

Pentobarbital produces respiratory depression and hemodynamic effects including a decrease in systemic vascular resistance, arterial pressure, cardiac output and a fall in coronary perfusion pressure.  Symptoms of toxicity include: circulatory depression, arrhythmias, respiratory depression, bronchospasm, emergence delirium, prolonged somnolence and recovery, nausea.

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