Some breeds of dogs are more prone to seizures than others, but seizures can happen to any dog.
Seizure treatment in dogs depends on the underlying cause, but phenobarbital is considered the first choice for chronic seizures.
Phenobarbital is a relatively safe and well-tolerated option for dogs with seizures, but your dog will need to have regular blood tests done while taking this medication.
A seizure is an uncontrolled and sudden electrical problem in the brain. Seizures can last for less than a minute or continue for several minutes. If you have ever seen your dog experience a seizure, it can be concerning and scary. Some dogs can appear distant or unresponsive and then suddenly fall to the floor. Your dog may also lose consciousness, look like they are trying to swim, or convulse.
While a seizure is a single event, epilepsy is when two or more seizures happen without a clear cause. Caring for a dog who has epilepsy can be stressful. Fortunately, veterinarians can prescribe medications to help control seizures in dogs. Phenobarbital is usually the first-choice medication for treating epilepsy. However, it may take some trial and error to decide whether it will work for your pet.
Here’s what you need to know about seizures in dogs and using phenobarbital to prevent them.
What causes seizures in dogs?
Certain breeds of dogs are more prone to seizures, including border collies, Labrador retrievers, beagles, and German shepherds. But, they can happen to any dog.
Eating poisonous items
Kidney or liver problems
Anemia (a low number of red blood cells)
If seizures don’t have an explainable cause, a vet may determine that your dog has epilepsy.
What are the signs of seizures in dogs?
A seizure can look different from dog to dog and from episode to episode. Seizures may be mild with few or no symptoms, but they can also cause more serious problems.
Symptoms of seizures in dogs include:
Collapsing or loss of consciousness
Twitching uncontrollably for a few seconds to several minutes
Stiffening or paddling of the limbs
Loss of bladder or bowel control
No response to touch or name-calling
Your dog may want to hide or appear dazed and stare into space shortly before a seizure starts. After a seizure is over, they may seem physically unstable and disoriented. Once a seizure has ended, and your dog is safe, contact your veterinarian or emergency pet hospital.
After a seizure, you will most likely be asked to bring your dog into the clinic or hospital for a thorough physical exam. The vet may discuss the potential causes and timing of your dog’s seizure, plus what happened before and after. Your veterinarian may also order blood tests and brain scans to provide them with more detail.
A single seizure that is fast-passing usually isn’t dangerous, but multiple episodes or very long-lasting seizures can be. If your pet has an average of two or more seizures per month, has a seizure that lasts longer than 5 minutes, or experiences a series of seizures within a single day, your vet will most likely prescribe medication to help prevent them. While there are a few options, phenobarbital is a common first choice for treating seizure conditions in dogs.
What is phenobarbital?
Phenobarbital is a prescription anticonvulsant (anti-seizure medication) that is available as an oral tablet, oral liquid, and injectable liquid. Veterinarians use phenobarbital as an off-label medication since it is not FDA-approved for use in dogs. Phenobarbital controls the electrical brain activity that happens during a seizure, helping to lower the number and severity of episodes.
Before prescribing phenobarbital, your vet may perform various blood tests to check your dog’s liver and kidney health. Vets do not typically prescribe this medication in dogs with known liver, kidney, or breathing problems, as the medication can worsen these conditions or cause dangerous side effects. If needed, phenobarbital can be used in combination with other seizure medications.
Phenobarbital is a controlled substance in the U.S., meaning there are more restrictions regarding how your pet’s prescription is filled at the pharmacy. This might include limits to the number of refills, limits to the amount of medication you can fill at once, and how long the prescription is valid. These regulations vary from state to state, so check with your local pharmacy for details.
How is phenobarbital administered in dogs?
In the clinic or hospital, phenobarbital may be given as an injection. Pet owners can fill a phenobarbital prescription as an oral tablet from any pharmacy. If your dog is having trouble with these, though, some pharmacies can compound personalized forms, such as pastes, oral liquids, or chewable tablets, to meet your pet’s needs.
You can give your dog phenobarbital with or without food. It should start working to fully control seizures within a few weeks, although you may begin to notice some improvement sooner than that. It’s important not to suddenly stop phenobarbital, as this can cause withdrawal symptoms, including a return of seizures.
How is a phenobarbital dose determined for dogs?
Your veterinarian will prescribe a dose based on a few factors, such as your dog’s weight and the number and severity of seizures they’ve been having. Typically, phenobarbital is started at a dose of 2.5 mg per kilogram of body weight every 12 hours. Depending on how your dog responds, this dose may be raised or lowered.
Timing of each dose is very important as missing even one dose can potentially trigger a seizure. If you accidentally miss giving a dose and it’s close to when you give the next dose, wait until the next dose is due and resume your dog’s usual medication schedule. Never give a double dose to try to make up for missed doses.
If you believe that your dog received too much medication, contact the American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center at (tel: 1-888-426-4435). Please note, a consultation fee may apply for the call.
What are the side effects of phenobarbital in dogs?
Phenobarbital is generally well-tolerated once your pet adjusts to the medication. Your dog may seem more tired than usual or uncoordinated when first starting phenobarbital or when the dose is raised. Some dogs, however, experience the opposite effect and may appear more restless or nervous. This might include actions like pacing around the room, panting, and whining.
Other common side effects of phenobarbital include:
A higher appetite
Drinking more water than usual
Urinating more often than usual
Weight gain (typically caused by eating more food)
These effects are usually temporary and get better or go away within a few weeks after your dog gets used to the medication. If your pet still seems very sleepy or uncoordinated after taking phenobarbital for 2 weeks, talk to your vet, as your dog may need a lower dose.
Rarely, a dog may develop anemia (low red blood cells) or have a sudden change in liver health. These are serious side effects. If you notice yellowing of the skin or eyes and vomiting at any point, contact your vet or go to an emergency animal hospital right away. These are signs of possible liver damage and need immediate medical care.
Does my dog need to be monitored while taking phenobarbital?
Yes. The veterinarian will regularly test your dog’s blood to check their phenobarbital levels. The ideal phenobarbital blood level is between 15 μg/mL and 35 μg/mL. If your dog’s levels come back lower or higher than this, the vet may change the phenobarbital dose and retest 2 weeks later.
Your dog’s liver health and red blood cells will also be checked to monitor for the serious side effects discussed above. These blood tests will be done more often when your dog first starts taking phenobarbital and then every 6 months once they are taking a steady dose and responding well.
Are there any drug interactions with phenobarbital and other medications?
Yes, many medications interact with phenobarbital. Certain antibiotics, such as metronidazole or doxycycline, will not work as well when taking phenobarbital. This is also true of theophylline (a medication used to open up the airways) and corticosteroids like prednisone.
Some medications may raise the risk of severe side effects with phenobarbital. Over-the-counter (OTC) antihistamines such as diphenhydramine or cetirizine can cause excessive drowsiness.
Medications for anxiety, such as alprazolam or cannabidiol (CBD), can lead to serious breathing problems. It’s important to note that these sedating medications may sometimes be used as an add-on seizure treatment when phenobarbital isn’t working well enough on its own. In these cases, it’s essential to follow your vet’s instructions very carefully to limit this drug interaction.
Lastly, the antibiotic rifampin can prevent phenobarbital from working properly. This could cause seizures or withdrawal symptoms if the two are taken together.
It’s important to note that these are not the only drug interactions for phenobarbital — just some of the most notable. Please provide your vet a complete list of all medications, vitamins, supplements, and herbal products your dog is taking before starting phenobarbital, so they can help your pet avoid any interactions.
What should I do if my dog continues to have seizures while taking phenobarbital?
Contact your vet immediately if your dog continues to have seizures after taking phenobarbital for 2 weeks. Seizures after this point may mean the dose is not right or that your dog needs a different medication.
Your veterinarian may recommend you give your pet an additional dose after a breakthrough seizure, but you should only do this with your vet’s instruction. Giving an extra dose on your own could be harmful to your dog.
It is helpful to keep a diary and record the length of the seizure, symptoms, and what happened right before and after the seizure occurred. Consider taking a video of your dog to share with the vet. This extra information may help your vet decide on the next steps for treating your dog’s seizures.
The bottom line
Phenobarbital is an anticonvulsant that can prevent seizures in dogs. It is generally well-tolerated and a common first-choice treatment. There are side effects to watch out for as well as several drug interactions. Give your dog phenobarbital as instructed, and take them for any ordered blood tests on time. Be sure to keep a log of any seizures your dog has, and speak to your vet if you have any concerns about their behavior or how phenobarbital is affecting them.
Was this page helpful?
Subscribe and save.
Get prescription saving tips and more from GoodRx Health. Enter your email to sign up.