Barbiturates

Older class of CNS depressants. Largely replaced by benzodiazepines and newer hypnotics such as zolpidem. Current main use as anticonvulsants, in treatment of migraines, and in reduction of cerebral edema and intracranial pressure resulting from head injury

• Screening

  • Immunoassays for automated chemistry analyzers

  • Urine

    • Target analyte—secobarbital

    • Cutoff concentration—200 or 300 ng/mL

    • Cross-reactivity—approximately 100% with amobarbital, 60–90% with butabarbital, butalbital, pentobarbital, and phenobarbital

  • Serum/plasma/blood

    • EMIT, ELISA, FPIA

    • Target analyte—secobarbital

    • Cutoff concentration—10–50 ng/mL ELISA; 1,000 ng/mL EMIT

    • Cross-reactivity—manufacturer kit reagent dependent:

      • Low cross-reactivity with amobarbital, phenobarbital, butabarbital, and butalbital and high cross-reactivity with thiopental and pentobarbital

      • FPIA generally demonstrates more cross-reactivity than EMIT to other barbiturates

Confirmation: chromatography or UV–visible spectrophotometry

• Sample pretreatment required

• Gas chromatography

• HPLC

• GC/MS

  • LC/MS

  • Limit of quantitation: analyte dependent—0.5–5.0 μg/mL