Seizures Dogs & Cats

Phenobarbital for dogs and cats

A long-used first-choice drug for epilepsy in dogs and cats. [1]

Last reviewed: October 2026 · 2 sources · see sources

Quick answerPhenobarbital is a prescription medicine for dogs and cats. A barbiturate that calms overactive brain signals. The most common side effects: sleepiness and wobbliness at first; more thirst, urination and appetite; raised liver values.

Key facts

Generic namePhenobarbital
Common brand namesLuminal
Used inDogs & Cats
TypeSeizures
Prescription?Prescription
Typical US priceNot listed (no reliable public source)

What it's used for

A long-used first-choice drug for epilepsy in dogs and cats. [1]

How it works

A barbiturate that calms overactive brain signals. [1]

Side effects and cautions

Common side effects: Sleepiness and wobbliness at first; more thirst, urination and appetite; raised liver values. [1]

Use with care: Liver checks and blood levels are needed. A controlled substance. Never stop suddenly. [1]

Call your vet right away if your pet has trouble breathing, facial swelling, hives, collapse, or any side effect that is severe or getting worse.

About dosingDosing is your vet's call. We don't list doses because the right amount depends on your pet's weight, age, health and other medicines. Don't change a dose or stop a medicine without asking your vet, and never give a pet medicine meant for people unless your vet tells you to [2].

What it costs

We don't list a price for this one because we couldn't find a reliable public source. Ask your vet or pharmacy for a quote; prices depend on your pet's size, the dose and where you fill it.

Phenobarbital FAQ

What is Phenobarbital used for in dogs and cats?

A long-used first-choice drug for epilepsy in dogs and cats.

What are the side effects of Phenobarbital?

Sleepiness and wobbliness at first; more thirst, urination and appetite; raised liver values.

Does Phenobarbital need a prescription?

Yes. It needs a prescription from a veterinarian.

How much Phenobarbital should I give my pet?

Only your veterinarian can tell you. The right dose depends on your pet's weight, health and other medicines, so we don't list doses. Never give a pet a medicine prescribed for a person or another animal without asking your vet.

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This page is general information for pet owners, not veterinary advice. Talk to your vet about your own pet.

Sources (2) — tap to show
  1. VCA Animal Hospitals – Phenobarbital (veterinary drug handout)
  2. FDA – Frequently asked questions about animal drugs