Phenobarbital
generic phenobarbital
Phenobarbital is the longest-established treatment for epilepsy in dogs and cats. It is an inexpensive human generic and a controlled substance, filled at ordinary pharmacies on a vet’s prescription, with blood-level monitoring to set the dose.
What it is used for
Phenobarbital raises the seizure threshold and is usually the first drug a vet reaches for when a dog or cat has repeated seizures. It is given twice a day, every day, and the dose is adjusted against a blood level measured a couple of weeks after starting and after any change. Liver function is checked regularly because long-term use can affect it.
Sedation, wobbliness, increased thirst, hunger and urination are common early and often settle. Levetiracetam, potassium bromide and zonisamide are the usual alternatives or add-ons when phenobarbital alone does not control seizures or causes problems. Missing doses can trigger seizures, so it should never run out or be stopped suddenly.
Safety points that differ from human use
- Never stop or skip doses without the vet; sudden withdrawal can cause severe seizures.
- Phenobarbital speeds up the liver’s handling of many other drugs, so doses of other medicines may need adjusting.
- An overdose causes deep sedation and breathing depression; store it securely and call poison control if a quantity is eaten.
- Tablets (human)
- Oral elixir (human; contains alcohol)
- Compounded flavoured liquids and capsules
- 15, 30, 60 and 100 mg tablets
- Compounded strengths to the vet’s prescription
Tablets come in enough strengths that most dogs can be dosed without compounding; cats often need a compounded liquid.
Why the cash price varies
Phenobarbital tablets cost pharmacies very little, so the cash price is dispensing fee and margin; because it is a Schedule IV controlled substance, refills are limited and the prescription must be renewed regularly, which means repeated fees. Not every pharmacy stocks every strength.
How to pay less
- Ask the vet for the largest quantity per fill the rules allow, to reduce dispensing fees.
- Ask the vet to write a strength the pharmacy stocks and that fits the dose without compounding.
- Ask whether phenobarbital is on the pharmacy’s flat-price generic list.
- Upload the prescription to Script Unlock so licensed pharmacies can quote. You pay the pharmacy directly.
Questions for your vet
- When will the blood level and liver tests be checked?
- What should I do if I miss a dose, or if my pet vomits after one?
- What should I do during a seizure, and when is a seizure an emergency?
- Does phenobarbital change the dose of my pet’s other medicines?
- How do I keep the prescription renewed so it never runs out?
Rules on refills, transfers and controlled substances differ by state; see pharmacy rules by state.
How Script Unlock gets you a cash price for your pet’s phenobarbital prescription
Prices on this site come from pharmacies responding to a real prescription. We do not publish estimated, average or "typical" prices, because none of those would be your price.
- 1You upload your prescription
A photo of your your pet’s phenobarbital prescription prescription is enough. Nothing is sold on the site; you are asking pharmacies to quote.
- 2Licensed pharmacies respond
Pharmacies that Script Unlock has verified see the request and each can reply with its own cash price for your exact drug, strength and quantity.
- 3You choose and pay the pharmacy
You compare the responses, pick a pharmacy, and pay that pharmacy directly when you collect. Script Unlock never takes a patient payment and never sets the price.
Related pet medications
Sources
- Merck Veterinary Manual
- ASPCA Animal Poison Control
- FDA Orange Book (approved generics and therapeutic equivalence)
- MedlinePlus drug information (National Library of Medicine)
Written by the Script Unlock editorial team from the sources above. Not yet reviewed by a veterinarian or veterinary pharmacist. Last checked 2026-10-03. Nothing here replaces your vet\u2019s directions; doses for animals are set by weight and species.
Script Unlock is a marketplace that lets licensed pharmacies quote a cash price on your prescription. It does not prescribe, dispense or sell medication, does not process patient payments, and does not give medical advice. Always follow the instructions of your prescriber and pharmacist and read the medication guide supplied with your medicine.