Barbiturate Toxicity Workup

Updated: Jan 23, 2021
  • Author: Keith A Lafferty, MD; Chief Editor: Michael A Miller, MD  more...
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Laboratory Studies

Obtain a complete blood cell count (CBC), electrolytes, BUN, creatinine, and glucose screen to distinguish barbiturate toxicity from metabolic derangements that can cause similar symptoms. An arterial blood gas (ABG) measurement may help establish the presence and progress of ventilatory failure, hypoxia, and metabolic acidosis. A serum lactic acid level may assess cellular hypoperfusion.

Quantify serum alcohol and barbiturate concentrations (particularly phenobarbital), if possible. Phenobarbital concentrations may be useful to determine the appropriate treatment and, once initiated, efficacy of treatment (eg, urinary alkalinization, multidose charcoal, hemodialysis).

A urine drug screen may help establish co-ingestants though its routine use rarely alters treatment and clinical outcome. Many clinicians routinely obtain acetaminophen and salicylate levels in all overdoses. This is particularly important because barbiturates/combination drugs may contain these analgesics.

Blood ethanol concentration may co-ingestants though its routine use rarely alters treatment and clinical outcome. Be aware of alcohol co-ingestion since a synergistic effect between alcohol and barbiturates may be expected.

Obtain a pregnancy test in women of childbearing age.

Barbiturate plasma concentrations aid in diagnosis and help determine whether to institute methods to enhance elimination and if so, whether these methods are effective. They are not accurate for predicting the duration or severity of toxicity. Considerations are as follows:

  • For short-acting barbiturates, a level of 35 mg/L carries an unfavorable prognosis.
  • For long-acting barbiturates, a level of 90 mg/L carries an unfavorable prognosis.
  • These levels do not apply to long-term barbiturate abusers.


Considerations regarding electrocardiography include the following:

  • In the hypothermic patient, awareness of any rhythm disturbances is important.
  • When the core temperature is below 30ºC (90ºF), risk of ventricular fibrillation is increased.
  • Higher toxic doses may induce bradydysrhythmias.