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Phenobarbital Side Effects in Dogs

Epilepsy and seizure disorders in dogs are scary. They often start without any warning, sometimes with a cause.  I know if my dog had a seizure, I would totally panic.

By the time you’re finished this post, you’ll have a better understanding of seizures, and the medications used to treat them, including phenobarbital.  

Most Common Breeds Prone to Seizures Include:

  • Australian shepherds
  • Beagles
  • Belgian Tervurens
  • Border collies
  • Boxers
  • Cocker spaniels
  • Daschunds
  • German shepherds
  • Golden retrievers
  • Irish setters.

Other dogs more likely to have seizures include:

  • Labrador Retrievers
  • Poodles
  • Saint Bernards
  • Shetland Sheepdogs
  • Siberian Huskies
  • Springer Spaniels
  • Welsh Corgies
  • Wirehair Fox Terriers
  • Vizslas.

Phenobarbital Side Effects in Dogs versus Seizure Activity

We often have no idea why some dogs start having seizures.

Sometimes it is linked to illness or trauma, but many times it just comes out of nowhere. One minute your dog is fine, the next they are having a seizure. 

Epilepsy, however, can occur in dogs of all ages.  Seizures may also be caused because of liver disease, brain tumors/trauma, or toxins (poisons) in the body.

As frightening as seizures can be, you may not need to take your dog in. The general protocol is three seizures in a 24-hour period.

Seizures in Dogs Might Not Look the Way you Expected Them to.

Dogs might foam at the mouth, twitch, drool, chomp, collapse and make paddling motions with their legs when having a seizure.

If your dog suddenly has a seizure for the first time, make sure he/she hasn’t gotten into something toxic or deadly, like rat poison or antifreeze.

How to Help Your Dog During a Seizure

Try to stay calm and quiet if you notice your dog having a seizure.  It’s not easy to do, but it will help your dog tremendously.

Move furniture out of the way and quickly move any other animals out of the room.  

Don’t try to put anything in your dog’s mouth when he/she is having a seizure.  There’s no need to hold your dog down either.

The seizure should stop as quickly as it started. 

As noted above, it could just be a one-time thing.  Frankly, I would still give the veterinarian a call just to see whether he/she recommends a visit.


Keep a Seizure Log!

The most common thing recommended to an owner whose dog has had seizures is that they keep a seizure log, listing the time of day and any activities that happened right before the event.

These logs can help in piecing together the reasons (triggers) for the seizure.

If you are concerned about phenobarbital side effects in dogs, consider keeping track of signs and symptoms.  These could come in handy at some point.

When a veterinarian recommends starting a dog on phenobarbital, it is usually because the seizures are frequent enough and strong enough to risk brain damage if the activity continues.

In a case like that, any side effects of phenobarbital in dogs is going to outweigh the risk of brain damage. 

If your dog continues to have seizures and the veterinarian prescribes phenobarbital, you might want to keep a checklist nearby for any unusual symptoms. 

Starting Phenobarbital- Common Side Effects

Phenobarbital is a controlled drug, and requires a prescription from a veterinarian.

It is a member of the barbiturate family, and works as a sedative and anticonvulsant (anti seizure) medication.

Vets usually don’t prescribe this medication lightly.

Phenobarbital side effects in dogs usually occur within the first few weeks.  If the dosage needs to be increased, you might notice more pronounced side-effects.

Most dogs develop a tolerance to the medication soon after starting it, and these side effects decrease or disappear.

READ: How Serious is Testicular Cancer in Dogs?

You Don’t Want to Miss Follow-Up Appointments, and Here’s Why:

Mild phenobarbital side effects in dogs are usually nothing to worry about. However, the veterinarian still needs to make sure that the dosage is appropriate and that the medication is working.

Sometimes, dogs with epilepsy require more than one medication to keep seizures under control.

Follow-up visits and blood work will measure levels of phenobarbital in their system, and will provide an indication of how the liver and kidneys are dealing with the medication.

Every animal (including humans) metabolizes phenobarbital differently, and so blood work is the only way to be sure the dosing is at the right level.

Maintaining the Phenobarbital Levels

You will be instructed to give your dog the medication every 12 hours, and it is important to give it as directed.

The goal is to reach a “therapeutic” level of phenobarbital in your dog’s blood.

Giving the medication on a more erratic schedule could lead to your dog having breakthrough seizures, where the amount of phenobarbital in the dog’s system drops too low.

Dosing on a different schedule can make your blood test results unreliable.

If you have missed doses, or given doses off schedule, then let your vet know this when you come in for blood work. They might want to postpone the test for a week while you focus on giving the medications correctly.

Never just stop giving phenobarbital! The medication can cause withdrawal symptoms, including severe seizures, if it is stopped suddenly.

Talk to your vet about how to wean your dog off phenobarbital safely.

READ: Von Willebrand’s Disease in Dogs – Information You Can Use

Other Options for Seizure Disorders

Phenobarbital is not the only medication that vets prescribe for seizures in dogs.

Potassium Bromide (KBr) is alternative that is frequently used, especially when phenobarbital isn’t working well or a dog is having severe side effects from the first medication.

Here’s Something You Should Know:

I’ve noticed that some websites list diazepam as an alternative medication for seizures, but this is a bit of a misunderstanding.

Diazepam is usually prescribed as an emergency medication for pets with severe and dangerous seizure disorders.

It is given (usually rectally) during a seizure event to stop a seizure and allow the owner time to rush the pet to an emergency clinic.

It is short acting (around 20 minutes), and it is not a medication given as a normal anticonvulsant preventative.

What About CBD Oil/Treats?

CBD oils, treats and potions for dogs are all over the internet, and they promise many miracle effects. So should you consider switching your dog from phenobarbital to a CBD product?

There have been NO laboratory studies proving that CBD works to prevent seizures in dogs. There are a LOT of anecdotes about CBD on the internet.

There is some research in humans that indicates the potential for CBD products to suppress some kinds of seizures.

So CBD could very well be a magic pill for dogs with seizure disorders. We just don’t know enough yet to say so with any certainty.

Since CBD products for dogs are usually supplements and not medications, they are not tested or monitored by any agency.

You really have no way to know that any given treat or oil contains what it says it contains, unless you are buying a product in a state that sells legal cannabis products. Often, these products undergo state mandated testing.

Switching from Phenobarbital to a CBD Product

If you decide you would like to try this kind of anti seizure therapy, I recommend you seek out a holistic or naturopathic veterinarian with experience in using CBD products.

They can guide you in making the switch safely, and can point you towards a product they have had good experiences with. Please, do not make this switch without the input of a Vet!

Seizures in dogs are scary, but they can be medically controlled. While phenobarbital side effects in dogs can be disturbing, they usually subside within a few weeks.

If your dog does not tolerate the phenobarbital, there are other options. Talk to your veterinarian…they are a great resource!

Thank you for reading this post. 

Special thanks to the writer of this post, Jen Clifford. Please check out her bio below!


Jen Clifford has a B.A. in Biology from Reed College.

She was a field biologist for several years and then spent 10 years working in veterinary medicine as a receptionist and technician.  Jen is currently a freelance writer living in the Pacific Northwest with her tribe of pets.

She is a passionate animal lover who is dedicated to helping people find solutions to their pet-related challenges. You can find more of her work on her website

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