Phenobarbital Side Effects in Dogs

If your precious pup is diagnosed with epilepsy, your veterinarian may prescribe phenobarbital to control seizures. While phenobarbital -- a barbiturate and anti-convulsant drug -- usually does the job, it's not without potential side effects. Your veterinarian will monitor your dog regularly during his treatment, including checking the rate at which he metabolizes phenobarbital through blood testing.

Close-up of a cute puppy, Lake of The Woods, Keewatin, Ontario, Canada
Watching your dog go through a seizure is scary, but phenobarbital can help.
credit: Keith Levit/Keith Levit Photography/Getty Images

Serious Side Effects

Rare but severe side effects of phenobarbital include liver toxicity or anemia. Because your vet monitors your dog carefully, checking liver function, she should discover either of these potential issues before permanent damage occurs. You'll bring your dog in for blood tests approximately a month after starting the medication and then every three to six months. Your vet checks the phenobarbital levels in the blood and performs a bile acid test to determine liver health. If side effects become severe, the vet can prescribe an alternative anti-epileptic medication.

Mild Side Effects

It's not uncommon for dogs who receive phenobarbital to sleep a great deal or become depressed or uncoordinated following initial treatment. Those side effects generally dissipate as the dog's body adjusts to the medication. Dogs on phenobarbital often experience increased thirst and appetite, and those side effects don't tend to lessen over time. You and your vet must decide whether those side effects outweigh phenobarbital's benefits.