Updated July 2026 · 8 min read

Phenobarbital 2026

Part of the ICU Emergencies Hub — browse every related guide in one place.

Phenobarbital is one of the oldest anticonvulsants still in daily ICU use. It's a long-acting barbiturate with two modern niches: refractory status epilepticus and severe alcohol withdrawal. Its strengths and its dangers both come from the same property — it works on GABA and it lasts a very long time.

Role 1: refractory status epilepticus

The status epilepticus ladder starts with a benzodiazepine (lorazepam), then a second-line agent (levetiracetam, fosphenytoin, or valproate). When seizures persist despite those, the patient is in refractory status and moves to anesthetic-dose infusions — and phenobarbital is one option in this space, alongside midazolam and propofol infusions. At these doses the patient is typically intubated, because the dose needed to suppress seizures also suppresses breathing.

Role 2: severe alcohol withdrawal

Benzodiazepines are first-line for alcohol withdrawal, but in benzodiazepine-refractory or severe cases (impending or actual delirium tremens, or patients needing escalating doses), phenobarbital is increasingly used. It reaches a different part of the GABA system than benzodiazepines and provides smooth, long-lasting control — its long half-life gives a self-tapering effect that can reduce breakthrough symptoms. Protocols vary widely; follow yours precisely.

Dosing and the loading principle

Phenobarbital is loaded IV to reach a therapeutic level, then maintained. IV administration must be given slowly — fast pushes cause hypotension and profound respiratory and CNS depression. Because the drug lasts days, dosing decisions compound: a dose that seems fine now keeps acting long after, so titration is deliberate and cautious.

Key properties at a glance

Nursing safety priorities

Push IV doses slowly and monitor blood pressure and respirations throughout. Watch cumulative sedation carefully given the long half-life. Be aware phenobarbital is a strong liver enzyme inducer that lowers levels of many co-administered drugs (a pharmacy-review issue). Protect the airway in status patients, and in withdrawal patients, track the withdrawal score to guide the protocol. As with any sedating anticonvulsant, oversedation and airway compromise are the events you're guarding against.

Related: lorazepam & the status ladder, levetiracetam, and midazolam.

This article is general educational information for licensed clinicians and students, not medical advice or a substitute for your institution's protocols, pharmacy guidance, or a provider's orders. Always follow facility policy and verify doses independently.