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Phenobarbital
Aka: Phenobarbital
- Indications
- Benzodiazepine Withdrawal
- Alcohol Withdrawal (second-line after Benzodiazepines)
- Status Epilepticus
- Seizure Prophylaxis
- Pharmacology
- Mechanism
- GABA A Receptor Agonist
- See Barbiturates for more detalied mechanism description
- Pharmacokinetics
- Half-Life: 53 to 140 hours (very long, self tapering in withdrawal)
- Onset (IV): 5 minutes
- Peak Effect (IV): 30 minutes
- Safety
- Pregnancy Category D
- Lactation: Not safe
- FDA Controlled Substance IV
- Therapeutic level: 15-40 mg/ml
- May be less addictive than Valium in outpatient withdrawal protocols
- Metabolism
- Liver Metabolism
- Renal Dosing: Decrease to twice daily for moderate to severe Renal Insufficiency
- Adverse Effects
- Serious
- Respiratory depression or apnea
- Intravenous dosing is higher risk for respiratory depression
- Avoid combining with Benzodiazepines or Opioids (see below)
- Withdrawal
- Avoid abruptly stopping
- Stevens-Johnson Syndrome
- Angioedema
- Suicidality
- Blood dyscrasias (Megaloblastic Anemia, Thrombocytopenia)
- Common
- Somnolence
- Bradycardia
- Nausea or Vomiting
- Dizziness, Nystagmus or Ataxia
- Decreased cognitive function
-
Drug Interactions
- CNS Depressants (Benzodiazepines, Opioids)
- Risk of respiratory depression or apnea
- Dosing
- Precautions
- Avoid IV infusion >60 mg/min
- Status Epilepticus
- Phenobarbital 20-30 mg/kg IV (infusion rate <=100 mg/min)
- Repeat dosing at 10 mg/kg every 1 hour as needed
- Epilepsy
- Phenobarbital 3 to 6 mg/kg/day divided 2-3 times daily, up to 50-100 mg orally twice to three times daily
- Alcohol Withdrawal
- Phenobarbital 5-10 mg/kg IBW up to 130 to 260 mg every 20-30 minutes titrating to light sedation
- Nisavic (2019) Psychosomatics 60(5):458-67 [PubMed]
- Nelson (2019) Am J Emerg Med 37(4):733-6 [PubMed]
- Tidwell (2018) Am J Crit Care 27(6):454-60 [PubMed]
- References
- (2020) Pharmacopeia, Tarascon, accessed on IOS 4/9/2021
- Cunningham and LoVecchio (2021) Crit Dec Emerg Med 35(4): 28