(961) Navigating Phenobarbital Use in Alcohol Withdrawal: Identifying and Addressing Toxicity

Introduction: Phenobarbital is commonly used in managing alcohol withdrawal due to its effectiveness in controlling symptoms and preventing seizures. It carries risk of toxicity, especially in patients with altered metabolism or underlying medical conditions. This report presents a case of phenobarbital toxicity following alcohol withdrawal treatment.

Description: A 61-year-old male with history of alcohol abuse presented with encephalopathy. On presentation, the patient was intubated due to hypercarbic respiratory failure. The toxicology screen was positive for benzodiazepines while CT head scan and EEG were unremarkable. He was treated for alcohol withdrawal with phenobarbital utilizing a Minnesota Detoxification Scale Assessment (MINDS) strategy. Following extubation, the patient experienced continued agitation and was treated with as needed phenobarbital dosing per facility protocol. Six days after admission, he developed a high anion gap metabolic acidosis with worsening encephalopathy and diminished brainstem reflexes concerning for phenobarbital toxicity. The diagnosis was confirmed by an elevated serum phenobarbital level of 44 μg/mL. Treatment involved discontinuation of phenobarbital, supportive care, and enhanced elimination through urine alkalinization with a sodium bicarbonate infusion targeting urine pH of greater than 7.5 and serum pH of less than 7.6. Over the next 2 days, there was significant improvement in the patients' mental status and he was transferred out of the intensive care unit.

Discussion: Phenobarbital, while effective in alcohol withdrawal treatment, can induce neurotoxicity and metabolic derangements through a variety of mechanisms. Toxicity may include, altered mental status, high anion gap metabolic acidosis, and hyperammonemia as illustrated in our case. Management involves cessation of phenobarbital, supportive care for respiratory depression and metabolic disturbances, and enhanced elimination through urine alkalinization with sodium bicarbonate. In severe cases, hemodialysis may be necessary. This case emphasizes the importance of vigilant monitoring for phenobarbital toxicity during alcohol withdrawal treatment. Early recognition of clinical signs, and a comprehensive, protocolized, management approach are essential for optimal patient outcomes.