Barbiturate (eg, phenobarbital) poisoning: Rapid overview of emergency management

To obtain emergency consultation with a medical toxicologist, in the United States, call 1-800-222-1222 for the nearest regional poison control center. Contact information for poison control centers around the world is available at the WHO website and in the UpToDate topic on regional poison control centers (society guideline links).

Clinical features

Common: CNS depression, hypoventilation, hypothermia.

Severe cases: Coma, loss of brainstem reflexes, hypotension, cardiovascular collapse.

Diagnostic evaluation

Fingerstick blood glucose
Serum electrolytes, creatinine, creatine kinase
Serum acetaminophen, salicylate, and ethanol concentrations to rule out these common co-ingestions
Electrocardiogram to screen for poisoning by drugs that affect the QRS or QTc intervals
Pregnancy test in females of childbearing age
Serum phenobarbital concentration in a patient with potential phenobarbital exposure

Management

Supportive care

CNS depression: Tracheal intubation may be required if the patient is unable to protect their airway or has hypoventilation.

Decreased respiratory rate and somnolent: Naloxone 0.04 to 0.4 mg (if breathing) or 1 to 2 mg (apnea) IV/IM or 4 or 8 mg IN per dose (children <5 years or ≤20kg: 0.1 mg/kg/dose IV/IO/IM; maximum 2 mg/dose or 4 or 8 mg IN/dose). Naloxone would not be expected to reverse the effects of the barbiturate itself, but may improve mental status or respiration if the patient has concomitant opioid intoxication.

Hypotension: IV isotonic saline or lactated Ringer (10 to 20 mL/kg, maximum 1 L) boluses. Vasopressors (eg, norepinephrine, phenylephrine) if no improvement.

Routine gastrointestinal decontamination with activated charcoal for isolated barbiturate ingestion is typically not needed since intoxication will improve with supportive care.

Phenobarbital ingestion with moderate to severe toxicity

Moderate toxicity: Depressed mental status that does not improve with verbal stimuli and a phenobarbital concentration >40 mcg/mL (172 micromole/L).

Severe toxicity: Hypotension requiring the use of vasopressors or cardiovascular collapse.

Multidose activated charcoal (MDAC):

Airway must be protected and no signs of ileus or bowel obstruction. Tracheal intubation should not be performed for the sole purpose of providing MDAC.
Place a nasogastric or orogastric tube.
The initial dose of activated charcoal is 50 g (adults) or 1 g/kg (pediatric; 50 g maximum) with or without cathartic.
Subsequent doses are 12.5 g per hour (adults) or 0.25 g/kg per hour (pediatric; 12.5 g maximum per hour), which can be administered continuously or in divided doses every two, four, or six hours (eg, 50 g every 4 hours), without a cathartic.

Alkalinize urine with sodium bicarbonate:

Bolus therapy: sodium bicarbonate, 1 to 2 mEq/kg (maximum 100 mEq) IV push over 3 to 5 minutes; repeat to achieve urinary pH goal.
Maintenance therapy: 150 mEq sodium bicarbonate in 1 L of D5W, run at 200 to 250 mL/hour in adults or run at 1.5 times maintenance in children.
Urine pH goal > 7.5 while maintaining serum pH <7.6
Correct hypokalemia, hypocalcemia and other electrolyte abnormalities.

Patient with severe toxicity or prolonged coma and/or increasing serum phenobarbital concentrations despite MDAC and urinary alkalinization: intermittent hemodialysis or continuous renal replacement therapy.

CNS: central nervous system; D5W: dextrose 5% in water; IM: intramuscular; IN: intranasal; IV: intravenous; MDAC: multidose activated charcoal; WHO: World Health Organization.

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Barbiturate (eg, phenobarbital) poisoning: Rapid overview of emergency management