II. Indications
- Benzodiazepine Withdrawal
- Alcohol Withdrawal (second-line after Benzodiazepines)
- Status Epilepticus
- Seizure Prophylaxis
III. 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
IV. Safety
V. Metabolism
- Liver Metabolism
- Renal Dosing: Decrease to twice daily for moderate to severe Renal Insufficiency
VI. 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)
- Respiratory depression or apnea
- Common
- Somnolence
- Bradycardia
- Nausea or Vomiting
- Dizziness, Nystagmus or Ataxia
- Decreased cognitive function
VII. Drug Interactions
-
CNS Depressants (Benzodiazepines, Opioids)
- Risk of respiratory depression or apnea
VIII. Dosing: General
- 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 for refractory Seizures
- Phenobarbital 20-30 mg/kg IV (infusion rate <=100 mg/min)
-
Epilepsy
- Phenobarbital 3 to 6 mg/kg/day divided 2-3 times daily, up to 50-100 mg orally twice to three times daily
IX. Dosing: Alcohol Withdrawal
-
General Dosing
- Phenobarbital 5-10 mg/kg IBW up to 130 to 260 mg every 20-30 minutes titrating to light sedation
-
Phenobarbital Single Agent Alcohol Withdrawal Protocol
- Indicated in Alcohol Withdrawal without use of Benzodiazepines or other CNS Depressants and neurologically intact
- Contraindicated with other CNS Depressants (e.g. Benzodiazepines)
- Protocol continued until patient is awake and calm
- IV Phenobarbital Load
- Phenobarbital 10 mg/kg Ideal Body Weight (IBW) over 30 minutes
- Wait 30 minutes before any additional Phenobarbital given
- IV Phenobarbital Titration
- Up to every 30 minutes give one of the 2 following doses as needed (no maximum, titrate to effect)
- Mild Symptoms: 130 mg IV over 3 minutes every 30 minutes as needed
- Severe symptoms 260 mg IV over 5 minutes every 30 minutes as needed
- Oral or IM Phenobarbital Maintenance (non-ED or ICU setting)
- Up to every 60 minutes give one of the 2 following doses as needed
- Mild Symptoms: 100 mg oral or IM every 60 minutes as needed
- Severe symptoms 200 mg oral or IM every 60 minutes as needed
- References
X. Resources
- Phenobarbital Tablet (DailyMed)
- Phenobarbital Injection (DailyMed)
XI. References
- (2020) Pharmacopeia, Tarascon, accessed on IOS 4/9/2021
- Cunningham and LoVecchio (2021) Crit Dec Emerg Med 35(4): 28
Images: Related links to external sites (from Bing)
Related Studies
phenobarbital (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
PHENOBARBITAL 100 MG TABLET | Generic | $0.32 each |
PHENOBARBITAL 15 MG TABLET | Generic | $0.18 each |
PHENOBARBITAL 16.2 MG TABLET | Generic | $0.18 each |
PHENOBARBITAL 20 MG/5 ML ELIX | Generic | $0.06 per ml |
PHENOBARBITAL 20 MG/5 ML SOLN | Generic | $0.06 per ml |
PHENOBARBITAL 30 MG TABLET | Generic | $0.19 each |
PHENOBARBITAL 32.4 MG TABLET | Generic | $0.23 each |
PHENOBARBITAL 60 MG TABLET | Generic | $0.27 each |
PHENOBARBITAL 64.8 MG TABLET | Generic | $0.29 each |
PHENOBARBITAL 97.2 MG TABLET | Generic | $0.38 each |
Ontology: Phenobarbital (C0031412)
Definition (CHV) | a drug used for epilepsy and anxiety |
Definition (CHV) | a drug used for epilepsy and anxiety |
Definition (NCI) | A long-acting barbituric acid derivative with antipsychotic property. Phenobarbital binds to and activates the gamma-aminobutyric acid (GABA)-A receptor, thereby mimicking the inhibitory actions of GABA in the brain. The activation effects of the phenobarbital-receptor-ionophore complex include increased frequency of chloride channel openings, membrane hyperpolarization and ultimately synaptic inhibition and decreased neuronal excitability. In addition, this agent inhibits glutamate induced depolarization. |
Definition (NCI_NCI-GLOSS) | A drug that is used to treat seizures and as a sedative. It is being studied in the treatment of diarrhea and for its ability to increase the antitumor effect of other therapies. It belongs to the family of drugs called barbiturates. |
Definition (MSH) | A barbituric acid derivative that acts as a nonselective central nervous system depressant. It potentiates GAMMA-AMINOBUTYRIC ACID action on GABA-A RECEPTORS, and modulates chloride currents through receptor channels. It also inhibits glutamate induced depolarizations. |
Definition (CSP) | barbituric acid derivative that acts as a nonselective central nervous system depressant. |
Definition (PDQ) | A long-acting barbituric acid derivative with antipsychotic property. Phenobarbital binds to and activates the gamma-aminobutyric acid (GABA)-A receptor, thereby mimicking the inhibitory actions of GABA in the brain. The activation effects of the phenobarbital-receptor-ionophore complex include increased frequency of chloride channel openings, membrane hyperpolarization and ultimately synaptic inhibition and decreased neuronal excitability. In addition, this agent inhibits glutamate induced depolarization. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=42405&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=42405&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C739" NCI Thesaurus) |
Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
MSH | D010634 |
SnomedCT | 255670005, 373505007, 51073002 |
LNC | LP14729-5, MTHU003431 |
English | Acid, Phenylethylbarbituric, Phenemal, Phenobarbital, Phenobarbitone, Phenylbarbital, Phenylethylbarbituric Acid, 2,4,6(1H,3H,5H)-Pyrimidinetrione, 5-ethyl-5-phenyl-, 5-Ethyl-5-phenyl-2,4,6(1H,3H,5H)-pyrimidinetrione, PHENO, phenobarbital (medication), Phenobarbitone - chemical, Phenobarbital [Chemical/Ingredient], PHENOBARBITAL, phenobarbitone, PHENobarbital, phenobarbital, Phenobarbitone - chemical (substance), Phenobarbitone product, Phenylethylmalonylurea, Phenobarbital (product), Phenobarbital (substance), Phenobarbital product |
Swedish | Fenobarbital |
Czech | fenobarbital |
Finnish | Fenemaali |
Russian | LIUMINAL, FENOBARBITAL, FENILBARBITAL, FENEMAL, FENOBARBITON, ЛЮМИНАЛ, ФЕНЕМАЛ, ФЕНИЛБАРБИТАЛ, ФЕНОБАРБИТАЛ, ФЕНОБАРБИТОН |
Japanese | フェネマール, フェニルエチルバルビツール酸, フェニルエチルマロニル尿素, エチルフェニルバルビツール酸, フェニルバルビトン, フェノバール, ワコビタール, フェノバルビタール, ルミナール, リナーセン, ルピアール, フェニルバルビタール, フェノバルビトン, ノーベルバール |
Italian | Acido feniletilbarbiturico, Fenilbarbital, Fenobarbitone, Fenobarbital |
Croatian | FENOBARBITAL |
Polish | Fenobarbital, Gardenal |
Spanish | fenobarbital - químico, fenobarbital - químico (sustancia), feniletilmalonilurea, fenobarbital (producto), fenobarbital (sustancia), fenobarbital, fenobarbitona, Fenobarbital, Fenemal, Fenilbarbital, Fenobarbitona |
French | Phénobarbital |
German | Phenemal, Phenobarbital, Phenobarbiton, Phenylbarbital |
Portuguese | Fenemal, Fenilbarbital, Fenobarbital, Fenobarbitona |