Barbiturates

GENERAL PRINCIPLES

• Barbiturates were once widely used as sedatives, anxiolytics, and hypnotics, but have generally been supplanted by the safer benzodiazepines.

• Barbiturates are still used in headache medications (Fioricet and Fiorinal), as anticonvulsants, in the treatment of alcohol withdrawal, and in certain limited circumstances for anesthesia and deep sedation.

Pathophysiology

• Barbiturates bind to the GABA-A receptor and directly induce opening of the chloride channel; this action is GABA-independent.

• Some barbiturates act as direct AMPA or NMDA glutamate antagonists.

• Barbiturates have anxiolytic, sedative, hypnotic, and anticonvulsant properties.

DIAGNOSIS

Clinical Presentation

• Barbiturate poisoning presents with coma, respiratory depression, and miosis.

• Hypotension and shock may occur in severe poisoning.

• Large cutaneous bullae called “barb blisters” may be present, especially when the patient has been down on a hard surface for a long period of time.

TREATMENT

• The mainstay of treatment is respiratory support, including intubation and mechanical ventilation in severe poisoning.

• If hypotension is present, treat with intravenous crystalloids and/or vasopressors.

• MDAC enhances the elimination of phenobarbital. ²⁵

î Administer MDAC only to patients with a protected airway (either spontaneously protected or secured by intubation).

• Urinary alkalinization with sodium bicarbonate was historically recommended for phenobarbital poisoning, but its efficacy is unclear.

• Hemodialysis effectively clears barbiturates and may be considered if prolonged coma, fluid­refractory shock, or respiratory depression necessitating intubation is present. Hemodialysis may also be considered in patients who do not improve with MDAC.