From the Guidelines
Management of phenobarbital toxicity requires prompt supportive care and specific interventions, with the primary goal of reducing morbidity, mortality, and improving quality of life. Initial management includes airway protection, ventilatory support if needed, and hemodynamic stabilization with IV fluids and vasopressors for hypotension.
- Activated charcoal (1 g/kg orally) should be administered if the patient presents within 1-2 hours of ingestion and has a protected airway, as it may help reduce absorption of the drug 1.
- For severe toxicity, multiple-dose activated charcoal (15-20 g taken orally every 6 hours) may enhance elimination, but its use should be cautious due to the risk of impaction and gut perforation 1.
- Urinary alkalinization is no longer recommended as first-line treatment in cases of barbiturate poisoning because it does not increase renal clearance significantly and MDAC is considered superior 1. In life-threatening cases, hemodialysis effectively removes phenobarbital and should be considered when levels exceed 100 mg/L or with severe clinical manifestations despite supportive care 1. Flumazenil is contraindicated as it doesn't reverse barbiturate effects and may precipitate seizures. Continuous monitoring of vital signs, neurological status, and serum phenobarbital levels is essential, with particular attention to respiratory depression, the most dangerous complication. Treatment should continue until clinical improvement occurs and phenobarbital levels fall below 40 mg/L. Phenobarbital has a long half-life (79-96 hours), so prolonged observation may be necessary even after apparent clinical improvement. The decision to perform ECTR should be based on clinical signs and symptoms of severe poisoning, rather than ingested dose and serum barbiturate concentrations alone 1.
From the FDA Drug Label
The toxic dose of barbiturates varies considerably. Barbiturate intoxication may be confused with alcoholism, bromide intoxication and various neurological disorders. For sedation, therapeutic blood levels of phenobarbital range from 5-40 µg/mL; the lethal blood level is greater than 80 µg/mL and usually ranges from 100-200 µg/mL Treatment of overdosage is mainly supportive and consists of the following: Maintenance of an adequate airway, with assisted respiration and oxygen administration as necessary. Monitoring of vital signs and fluid balance Fluid therapy and other standard treatment for shock, if needed. If renal function is normal, forced diuresis may aid in the elimination of the barbiturate. Alkalinization of the urine increases renal excretion of phenobarbital. Although not recommended as a routine procedure, hemodialysis may be used in severe barbiturate intoxication or if the patient is anuric or in shock Hemoperfusion through an anion-exchange resin or activated charcoal has been successful.
Management of Phenobarbital Toxicity
- Maintain an adequate airway with assisted respiration and oxygen administration as necessary
- Monitor vital signs and fluid balance
- Provide fluid therapy and standard treatment for shock if needed
- Consider forced diuresis if renal function is normal
- Alkalinization of the urine may increase renal excretion of phenobarbital
- Hemodialysis or hemoperfusion may be used in severe cases 2 Key considerations include:
- Patient should be rolled from side to side every 30 minutes
- Antibiotics should be given if pneumonia is suspected
- Appropriate nursing care to prevent hypostatic pneumonia, decubiti, aspiration and other complications of patients with altered states of consciousness
From the Research
Management of Phenobarbital Toxicity
The management of phenobarbital toxicity involves several strategies to enhance the elimination of the drug from the body. Some of the key approaches include:
- Urinary alkalinization: This method involves increasing the pH of the urine to increase the excretion of phenobarbital 3
- Multiple-dose activated charcoal: This approach involves administering repeated doses of activated charcoal to absorb the drug and prevent its reabsorption into the bloodstream 3, 4, 5
- Supportive care: This includes cardiac and respiratory support, as well as the use of cathartics and alkaline diuresis 6
- Extracorporeal therapy: In severe cases, hemodialysis and hemoperfusion can be used to enhance drug clearance, and continuous renal replacement therapy may be considered if the patient's circulation is unstable 6, 7
Comparison of Treatment Modalities
Studies have compared the efficacy of different treatment modalities for phenobarbital toxicity. For example:
- A study found that multiple-dose activated charcoal was superior to urinary alkalinization in enhancing phenobarbital elimination 3
- Another study found that repeated doses of activated charcoal significantly increased the elimination of phenobarbital, but had no clear effects on the patients' clinical course 5
- A case report described the successful treatment of a patient with severe phenobarbital poisoning using continuous renal replacement therapy 7
Clinical Considerations
The management of phenobarbital toxicity requires careful consideration of the patient's clinical condition and the severity of the overdose. For example: