Most cats that seize once never seize again, and most that do seize repeatedly can be controlled with one drug and a clear monitoring schedule. Two numbers decide everything: how long a seizure lasts, and how many happened in 24 hours. Five minutes or longer, or two or more in a day, is status epilepticus territory and needs a vet now. Everything else is diagnosis, then dose, then follow-up.
Focal or generalized
Generalized seizures are the ones people recognize: the cat falls on its side, legs paddle, jaw chatters, pupils dilate, and it urinates or defecates. It lasts 30 to 90 seconds, then there is a 5 to 30 minute period of disorientation, pacing, and temporary blindness. Focal seizures are easier to miss: one limb twitches, the face pulls to one side, the cat flies at an invisible object, or it has 10 to 20 seconds of lip smacking and head turning.
Focal seizures matter because they often point at a structural lesion — a tumor, a scar, encephalitis — on one side of the brain. A cat with a focal seizure starting at age 12 has a very different workup than a 4-year-old with a single generalized event. Both get an exam, but only the first is a strong candidate for MRI.
When a seizure is an emergency
Time it. A seizure lasting more than 5 minutes, or 2 or more within 24 hours, is the threshold for emergency treatment, because prolonged seizure activity causes brain swelling, high body temperature, and low blood oxygen. Cats can also seizure so continuously that the movements look subtle — just a twitching face and a fixed stare for 20 minutes.
What to do during one: clear hard objects away, dim the lights, do not put anything in the mouth, and do not restrain the cat beyond keeping it from falling. Do not touch the back of the head or neck. Note the start time and record video if you can, because a 15-second clip tells the vet more than a paragraph. Cooling with a fan and cool water on the paws helps if the body temperature goes above 39.5°C, but never use ice. Emergency first steps are covered in cat seizure first aid.
What to check before starting drugs
Not every seizure needs medication. Most vets treat when there are 2 or more seizures in 6 months, when a seizure lasts over 5 minutes, when clusters occur, or when a structural lesion is found. Before the first pill, baseline bloodwork matters: a chemistry panel, complete blood count, bile acids or ammonia, blood pressure, and a thyroid level in cats over 8.
Age changes the plan. A first seizure in a cat under 6 is more often metabolic or toxic — antifreeze, permethrin flea products, lead, organophosphates, or low blood sugar from an insulin overdose. A first seizure in a cat over 8 should prompt imaging: MRI is the only way to see a meningioma, and those are common in older cats and sometimes surgically removable.
Phenobarbital: dose, timing, and levels
Phenobarbital is the first-line drug in cats. The usual starting dose is 2 to 4 mg per kg every 12 hours, and starting at the low end of that range is common because cats clear the drug slowly. Steady state is reached in 10 to 14 days, so a level drawn before day 10 is not interpretable.
The target blood level is 15 to 45 μg/ml. Below 15, most cats still seize; above 45, sedation, stumbling, and appetite loss climb quickly. If seizures continue at a level of 20, the next move is usually adding a second drug rather than pushing phenobarbital higher, because the side-effect curve is steep. Give the pill with food at the same times daily, and never stop abruptly — withdrawal can trigger clusters.
Levetiracetam as the add-on
Levetiracetam, usually 20 mg per kg three times daily, is the most common second drug. It has almost no liver metabolism, so it is the choice for a cat with liver values already rising, and it works within hours, which makes it useful for cluster control. The trade-off is the dosing interval: three times a day is hard for a working owner, and an extended-release form given twice daily costs more.
Other options exist — zonisamide, gabapentin as a partial add-on, potassium bromide, which is used less in cats because of asthma-like side effects. Whichever is chosen, the test is the same: a seizure log showing whether the interval between events lengthened.
Liver risk and the 6-month check
Phenobarbital is metabolized by the liver and induces liver enzymes, so ALT and ALP rise on treatment in most cats without meaning damage. What matters is the trend plus bile acids. A reasonable schedule is a full panel at 2 weeks, 3 months, then every 6 months, with a phenobarbital level at the same visits.
Signs that should move the visit sooner: appetite loss, vomiting, yellow gums, weight loss, and a cat that seems drunk between doses. Cats also develop phenobarbital tolerance, so a dose that worked at month 3 may not hold at month 12, and the level will show it before the seizures do. Senior cats need the same panel interpreted against their kidney values — see senior cat care.
What the log buys you
| Record | Why it changes decisions |
|---|---|
| Date and clock time | Shows whether intervals are lengthening over 8 to 12 weeks |
| Duration in seconds | Anything over 120 seconds argues for a dose change |
| Focal or generalized | A shift from generalized to focal, or the reverse, suggests a new lesion |
| Recovery time | Longer post-ictal confusion suggests the seizure was more severe |
| Possible trigger | Missed dose, stress, heat, new medication |
Two or more seizures in one week, any seizure over 5 minutes, or a cat that does not return to normal within an hour are the three findings that should trigger a call rather than a wait.
What to do this week
- Start a log with date, time, duration, and what the cat did before and after.
- Film one episode on your phone if it is safe to do so.
- Book baseline bloodwork before the first dose of phenobarbital, including bile acids.
- Set two daily alarms 12 hours apart and keep pills by the food bowl so doses are not missed.
- Book the 2-week level, then the 3-month panel, then every 6 months.
Frequently asked
Can a cat live a normal life on phenobarbital?
Most do. Sedation is worst in the first 2 to 3 weeks and usually fades as the cat adapts. The main long-term costs are twice-daily dosing, bloodwork every 6 months, and watching for appetite loss or wobbliness. Cats that stay below a level of 45 ug/ml generally keep normal activity and grooming.
Should I give an extra pill after a seizure?
Not without asking the vet. A common plan for cluster seizures is an extra dose or a rescue medication such as intranasal midazolam or rectal diazepam, but that plan has to be written for your cat in advance. Doubling a phenobarbital dose on your own risks heavy sedation and liver strain without stopping the cluster.
Does a first seizure at 12 years old mean a brain tumor?
Not always, but the odds are high enough that imaging is worth discussing. In cats over 10, structural disease accounts for a large share of first seizures, and meningioma is the most common tumor found. Bloodwork comes first to rule out metabolic causes; MRI or CT is the next step if those are normal.