Phenobarbital
Phenobarbital is a long-acting barbiturate antiepileptic medication used primarily to control generalized and partial seizures. It works by enhancing the effects of GABA, an inhibitory neurotransmitter in the brain, thereby reducing neuronal excitability. While effective, it is typically reserved for specific seizure types when newer agents are not suitable due to its side effect profile and potential for dependence.
Phenobarbital is an older antiepileptic drug used to control seizures by enhancing GABA activity in the brain.
Key facts at a glance
- ATC
- N03AA02
- RxNorm
- 8134
- Generic
- Phenobarbital
- Class
- atc-n03
- Brands
- Donnatal, Phenohytro, Sezaby, Fidoquel
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- injection, solution, tablet, capsule
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 50-100mg 2-3 times daily
- Maximum
- consult physician
- Frequency
- every 8-12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 3-5mg/kg daily in divided doses
- Maximum
- consult physician
- Frequency
- every 8-12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 50mg once daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesteravoid if possible
avoid use during pregnancy unless benefits outweigh risks - associated with increased risk of congenital malformations
regular fetal monitoring, ultrasound for anomalies
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
third trimesteravoid if possible
discontinue if possible before delivery or use lowest effective dose
fetal monitoring, assess for neonatal withdrawal
Use of this medication in this population requires careful consideration of risks and benefits.
lactation
breastfeedingavoid
breastfeeding not recommended - drug excreted in breast milk
monitor infant for excessive sedation, poor feeding
Use of this medication in this population requires careful consideration of risks and benefits.
pediatric_age
infantsweight-based dosing required
use with extreme caution - start at low dose and titrate slowly
regular serum level monitoring, monitor for sedation and respiratory depression
Use with caution and monitor for adverse effects.
pediatric_age
childrenweight-based dosing required
use for refractory seizures only - not first-line therapy
regular serum level monitoring, cognitive and developmental assessment
Use with caution and monitor for adverse effects.
geriatric
elderlyreduce dose, start low
use lowest effective dose due to increased sensitivity and reduced metabolism
monitor for falls, confusion, sedation, serum levels
Use with caution and monitor for adverse effects.
renal_impairment
severe ckddose reduction may be needed
use with caution - drug primarily hepatically metabolized but metabolites excreted renally
monitor serum creatinine, consider therapeutic drug monitoring
Use with caution and monitor for adverse effects.
hepatic_impairment
severesignificant dose reduction required
avoid if possible - extensively metabolized in liver
therapeutic drug monitoring essential, monitor liver function
Use of this medication in this population requires careful consideration of risks and benefits.
Statistics and clinical data
Drug class
Central nervous system depressant, first-generation barbiturate
Primary therapeutic use
First-line treatment for certain seizure disorders
Controlled substance schedule
Regulatory classification in the United States
First approved
Historical approval information for seizure control
Treatment of generalized tonic-clonic seizures, partial seizures, status epilepticus, and febrile seizures in children. Also historically used for sedation and anxiety, though these uses have largely been replaced by safer alternatives.
Enhances GABAergic neurotransmission by binding to barbiturate sites on GABA-A receptors, increasing the duration of chloride channel opening and producing neuronal hyperpolarization, which reduces seizure activity.
May cause drowsiness, dizziness, and cognitive effects. Has significant drug interactions and narrow therapeutic index requiring blood level monitoring. Risk of physical dependence with prolonged use. Avoid abrupt discontinuation as it may precipitate seizures. Contraindicated in patients with porphyria, severe respiratory insufficiency, and should be used cautiously in pregnancy due to risk of fetal harm.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 24, 2026. · Read our editorial policy