Phenobarbital for Dogs with Seizures: What to Know - GoodRx (2024)

Key takeaways:

  • 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.

Phenobarbital for Dogs with Seizures: What to Know - GoodRx (1)

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.

Sometimes, seizures are caused by other conditions or illnesses like:

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

  • Jaw-chomping

  • Drooling or foaming at the mouth

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.

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Phenobarbital for Dogs with Seizures: What to Know - GoodRx (2024)


What is the ideal phenobarbital level for dogs? ›

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.

What are the dangers of phenobarbital in dogs? ›

Are there any potential side effects? Common side effects in dogs include anxiety, agitation, lethargy, or sedation when therapy is started, and increased thirst, urination, and appetite or elevated liver enzymes on bloodwork are possible. Side effects such as incoordination may indicate a dose that is too high.

What if my dog is on phenobarbital and still having seizures? ›

While the majority of dogs respond very well to Phenobarbital and/or potassium bromide, there are a few dogs that will continue to have a high seizure frequency despite having adequate serum levels of these medications, and are called “refractory”. For these dogs newer anticonvulsants may help.

What medication will work with phenobarbital for dogs with seizures? ›

In some cases, phenobarbital is used concurrently with levetiracetam for the management of seizures in dogs. Phenobarbital for dogs increases the metabolism of levetiracetam, so the levetiracetam dose may need to be adjusted and increased when phenobarbital is added.

How often should you check phenobarbital levels? ›

Common labs for monitoring phenobarbital

We will usually recommend checking a phenobarbital level 4 weeks after reaching a therapeutic dose and then every 4-12 months thereafter.

How long can a dog stay on phenobarbital? ›

Since treatment with phenobarbital is generally life-long, monitoring blood tests are periodically recommended. Phenobarbital is generally effective regardless of the underlying cause of the seizure disorder which means that is can be used for epilepsy, brain tumors, infectious diseases, or poisonings.

Is there an alternative to phenobarbital for dogs? ›

Potassium bromide and imepitoin can be used as alternative monotherapies to phenobarbital and are the first line adjunctive anti-epileptic drugs.

How do dogs act on phenobarbital? ›

Being a drug that acts on the brain, phenobarbital has side effects involving the nervous system. Soon after starting, your dog may sleep more than usual. They may also be somewhat clumsy, tripping and bumping into doors and furniture. Your dog on phenobarbital may seem more thirsty and hungry than before.

What are some common problems with those on phenobarbital? ›

Adverse Effects
  • Nervous System: Agitation, somnolence, confusion, CNS depression, hyperkinesia, ataxia, nervousness, nightmares, psychiatric disturbance, thinking abnormality, insomnia, anxiety, hallucinations, dizziness.
  • Respiratory System: Apnea, hypoventilation.
  • Cardiovascular System: Hypotension, bradycardia, syncope.
Jan 17, 2022

How long do dogs with epilepsy live? ›

Approximately 40-60 percent of dogs with epilepsy have one or more episodes of cluster seizures or status epilepsy, and a mean lifespan of only 8 years, compared to 11 years for those with epilepsy without episodes status epilepsy.

What happens when your dog won't stop having seizures? ›

If a seizure lasts more than three to five minutes, this is an emergency and you should bring your dog to a veterinarian. Their body temperature can rise quickly and can be a problem. Especially as pets age, seizures that last that long can cause problems with their brain and cause brain damage.

What are the long term side effects of phenobarbital? ›

Cognitive deficits in adults: Long-term use of phenobarbital is associated with a number of cognitive deficits in adults that can include similar issues with learning and memory, attention and concentration, complex attention, expressive and receptive speech, and problem-solving.

What is the most effective seizure medication for dogs? ›

Phenobarbitone is often the preferred first choice as it takes effect more quickly (within 2 weeks) than Potassium Bromide (3 to 6 months). Potassium Bromide can be used as first choice in animals with pre-existing liver disease or animals with very low seizure frequency.

Is Keppra safer than phenobarbital for dogs? ›

Keppra differs from traditional anti-seizure medication in the fact that it does not contain either Potassium Bromide or Phenobarbital, which means it has a wider margin of safety, especially for dogs suffering from a damaged liver, or liver problems.

What are alternatives to phenobarbital for seizures? ›

What are some common antiepileptic drugs?
  • Phenobarbital (Luminal) This is one of the oldest central nervous system drugs used to control seizures. ...
  • Phenytoin (Dilantin) ...
  • Topiramate (Topamax) ...
  • Zonisamide (Zonegran) ...
  • Lamotrigine (Lamictal) ...
  • Levetiracetam (Keppra) ...
  • Clonazepam (Klonopin) ...
  • Lorazepam (Ativan)
Feb 28, 2022

What is the toxic range of phenobarbital? ›

The therapeutic reference range of phenobarbital is 10-30 mcg/mL. The toxic reference range of phenobarbital is >40 mcg/mL.

What is the dosing range for phenobarbital? ›

For phenobarbital
  • For oral dosage forms (elixir, capsules, or tablets): For trouble in sleeping: Adults—100 to 320 milligrams (mg) at bedtime. Children—Dose must be determined by your doctor. ...
  • For injection dosage form: For trouble in sleeping: Adults—100 to 325 mg, injected into a muscle or vein, or under the skin.

What is phenobarbital 10mg for dogs? ›

Veterinarians use phenobarbital to treat dogs having seizures. The drug is categorized as a barbiturate. Phenobarbital is used to treat your dog if they have epilepsy or other seizures. This drug stabilizes the brain cells and prevents the unregulated electrical discharges in the brain that cause seizures.

What is phenobarbital 45 mg for dogs? ›

Key Takeaway: In dogs, Phenobarbital is usually prescribed for seizure disorders such as epilepsy. Some of its side effects include agitation, anemia, anxiety, increased thirst or appetite, lethargy, liver damage from long-term use, incoordination, restlessness, sedation, and weight gain.


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