Seizures and epilepsy in dogs and cats
Repeated seizures without another cause are epilepsy, common in dogs and less so in cats. Treatment is a daily anti-seizure medicine for life, phenobarbital or levetiracetam first, with potassium bromide or zonisamide added if needed. All are human generics filled at ordinary pharmacies, two of them controlled substances.
What it is
A seizure is a burst of abnormal brain activity: collapse, stiffening, paddling, drooling and loss of awareness for a minute or two, followed by confusion. A single seizure is investigated; repeated seizures with no cause found on blood tests and, often, MRI are called idiopathic epilepsy, which usually starts between one and five years of age in dogs and runs in some breeds. In cats, and in older dogs, a brain tumour, liver disease or other illness is more often the cause and is treated directly.
Treatment starts when seizures are frequent, severe or clustering. The aim is fewer and milder seizures with acceptable side effects, not necessarily none. Owners keep a seizure diary, learn what to do during a seizure, and know when a prolonged seizure or a cluster means an emergency trip.
How it is treated
Phenobarbital is the traditional first drug: effective, cheap, twice daily, with blood levels and liver tests to guide the dose. Levetiracetam is the other first choice, with few side effects and no monitoring, but a short duration that means three doses a day unless the extended-release tablet suits the dog. Many dogs end up on both.
Potassium bromide, compounded or bought as a veterinary product, is an older add-on for dogs (not cats). Zonisamide, a human generic, is a newer add-on. For clusters at home, the vet may prescribe rectal or nasal diazepam or midazolam, or a short course of extra levetiracetam. Dietary supplements and prescription diets have some evidence as adjuncts.
What an owner pays cash for
An epileptic dog or cat is on medicine every day for life, so the per-tablet price and the number of dispensing fees matter more than for almost any other condition. Phenobarbital and levetiracetam are commodity generics, but phenobarbital is a controlled substance with limited refills, so prescriptions are renewed often; levetiracetam at three doses a day for a large dog means a high tablet count. Blood-level and liver monitoring is the other recurring cost. A flat-price pharmacy, the largest fill the rules allow, and a strength that fits the dose without compounding are where owners save.
The medicines, one guide each
- PhenobarbitalPharmacy can fill
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.
- LevetiracetamPharmacy can fill
Levetiracetam is a human anti-seizure drug now widely used in dogs and cats, alone or added to phenobarbital, because it has few side effects and needs no blood-level monitoring. It is an inexpensive generic that any pharmacy can fill.
- ZonisamidePharmacy can fill
Zonisamide is a human anti-seizure drug used in dogs, and occasionally cats, as an add-on when phenobarbital or levetiracetam alone is not enough, or as a first drug for dogs that cannot take phenobarbital. It is a generic capsule that any pharmacy can fill, and it has become much cheaper than it once was.
- Potassium bromideVet-only
Potassium bromide is an old anti-seizure drug used in dogs, usually added to phenobarbital or levetiracetam when seizures are not controlled, and sometimes alone in dogs with liver disease. It has no human product, so it is dispensed as a conditionally approved veterinary chewable or compounded by a pharmacy. It is not used in cats.
Questions for your vet
- Has another cause been ruled out, and is an MRI advisable?
- Phenobarbital or levetiracetam first for my pet, and why?
- What do I do during a seizure, and when is it an emergency?
- What monitoring is needed, and how often?
- How do I keep a controlled prescription renewed so it never runs out?
How Script Unlock gets you a cash price for your pet’s prescription
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Sources
Written by the Script Unlock editorial team from the sources above. Not yet reviewed by a veterinarian. Last checked 2026-10-03. Your vet\u2019s diagnosis and plan come first; nothing here replaces them.
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.