Phenobarbital for Dogs: Treating Canine Seizures

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By: Kathryn Anderson Updated: April 17, 2020

Phenobarbital for Dogs with seizuresPhenobarbital for dogs is an important medication used to control seizure in dogs and cats. It works by making brain cells more resistant to abnormal electrical activity. Treatment with phenobarbital aims to reduce the number and severity of seizures, but may not eliminate fits altogether.

Phenobarbital was one of the first anti-seizure medications to be developed. With a proven track record of effectiveness, your vet is likely to choose it as the drug of choice to manage epilepsy.

But all drugs have side effects and phenobarbital is no different. It causes sedation and wobbliness until the dog gets used to the drug. And in the long term, adverse effects include liver damage.

What is Phenobarbital for Dogs?

Phenobarbital belongs to a family of drugs called the barbiturates. In particular, phenobarbital is a long-acting barbiturate that has an anticonvulsant action. This simply means the drug stays in the body a long-term and helps reduce seizure activity.

This veterinary medicine comes in tablet and liquid form. It is a prescription only medication, which means only a vet can provide it or issue a written prescription for phenobarbital tablets or liquid.

Take care to keep all anti-seizure medications, including phenobarbital, out of the reach of children and other pets in the house.

Epilepsy in Dogs

Many pet owners are familiar with the term ‘epilepsy’ but unaware of the precise meaning.

Seizures in dogs can be caused by any number of underlying health conditions. Examples include a liver shunt, toxin ingestion, or a brain tumor. However, when the seizures have been investigated and no underlying cause is found, then and only then is the condition considered to be epilepsy.

Dogs with epilepsy may have clusters of seizures (a group of fits occurring within 24 – 48 hours) which are mild or severe. The worst fits are when the dog enters a seizure which doesn’t end. This life-threatening development is called status epilepticus.

Epilepsy medications for dogs 

Seizures are deeply unpleasant for the dogs and distressing for the owner. To alleviate this, it’s important to reduce seizure frequency and severity. Sometimes phenobarbital does the trick, but other times an add-on treatment is required.

This is usually another antiseizure medication from a different family of drugs. Examples of these antiepileptic drugs include potassium bromide, zonisamide, and levetiracetam.

Treating Epilepsy in Dogs and Canine Seizures with CBD Oil for Dogs

There is a lot of buzz about the use of CBD oil to treat seizures in dogs.  In human medicine, this is an ongoing area of research. But you veterinarian may seem hazy about the benefits of CBD oil.

This is because legislation about cannabis use leaves your vet liable to prosecution should something go wrong. Also, that same legislation makes undertaking meaningful research and clinical trials exceedingly difficult. Therefore, sadly, not enough is known about CBD oil’s potential for good.

What is CBD Oil?

CBD is an abbreviation of the word cannabidiol. CBD is derived by processing hemp (the rope-like stuff) or cannabis (the recreational drug). Drugs such as cannabis give people a ‘high’ because of the presence of psychoactive substances called tetrahydrocannabinol (THC).

However, CBD oil does not have any mind-altering properties and only used for medical reasons. Anecdotally it is used to help chronic pain, seizure conditions, and anxiety issues. Because of the lack of monitored clinical trials, at the moment in the veterinary field, the effects are purely anecdotal and not proven.

CBD Oil for Dog Seizures: CBD Oil Drug Interactions

There is little evidence-based advice about combing CBD oil with other medications. Therefore, be careful if you decide to give it a go. Speak to your vet first, so they are aware of the potential for destabilization.

Also, never stop phenobarbital suddenly. This can trigger serious seizure activity. Also, dose reductions of phenobarbital can allow seizures to break through, so be aware of this.

The decision to trial CBD oil for seizures requires careful consideration. Whilst anecdotally it can be helpful, there is no scientific proof of this in pets.

In addition, the effect on the dosage of phenobarbital is unknown. This could risk interfering with how phenobarbital works and seizures breaking through, or CBD causing increased phenobarbital levels and profound sedation.

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Honest Paws: Natural Epilepsy Medications for Dogs?

Another factor to consider is the purity of the CBD oil. The purification process is unregulated. Some forms of CBD oil may contain residues of the chemicals used to extract the oil. Also, the levels of CBD may not be as high as stated on the label.

When considering a CBD oil look for one, such as Honest Paws, that refines to a high standard. This reduces the risk of accidentally dosing your dog with harsh chemicals, in addition to the CBD.

Phenobarbital High: Can My Dog Get Addicted to this Drug?

Epileptic dogs treated with phenobarbital do need to be carefully monitored and managed. There are a number of reasons for this.

Firstly, phenobarbital for dogs works best when it reaches a steady-state concentration in the blood at a therapeutic dose.  This therapeutic range is relatively narrow. Your veterinarian assesses the drug dosage based on seizure recurrence and blood tests looking at serum levels of phenobarbital and liver enzymes.

The blood level of phenobarbital needs to stay steady, which means regular doses. This ideal dosage interval is every 12 hours. If a dose is late, blood levels can fall. This can allow seizures to break through.

dog taking phenobarb for canine seizure 

Phenobarbital is a long-term treatment and drug withdrawal (for whatever reason) must be gradual. Always consult your veterinarian before making dosage adjustments.

A sudden change, such as stopping treatment medication can lead to serious, recurrent seizures in dogs.

My Dog is Acting Drunk and Wobbly: Phenobarbital Side Effects in Dogs

The effects of phenobarbital in a naive pet can be upsetting for an owner to witness. This medication is a sedative and when given for the first time the dog is likely to appear dopey, acts drunk, and is wobbly. Happily, this effect is usually temporary and wear off as the pet gets used to the medication.

If the pet is excessively sleepy, the veterinarian may check blood phenobarbital levels to reassess dosage. For dogs that act permanently drunk, the vet may decide to combine two different anticonvulsant medications, each given at a reduced dosage.

Other less common side effects include a drug rash. Even more unusual is a type of eye tick, where the eyes flick from side to side.

Sadly, phenobarbital is also liver toxic. When given at high dosages for a long time it causes liver damage. This is detectable on blood tests. When caught early, a dose reduction can allow the liver to recover.

Contraindications: What Dog Should Not be Using this Medication?

Given that phenobarbital for dogs has such serious side effects, it should be used with care. Your veterinarian will carefully asses any other medications the pet is taking, to ensure there is no interaction.

Some medications can increase the ‘strength’ of phenobarbital, so combining the two is unwise. Drugs that are best avoided in combination with phenobarbital include griseofulvin, chlorambucil, and some antihistamines.

On the other hand, some drugs interfere with phenobarbital and make it less effective. Examples of the drugs your vet will avoid combining include beta-blockers, metronidazole, and some steroids.

Drug interactions aside, epileptic dogs with pre-existing liver disease should avoid taking this medication.

white pup getting treated for seizures in dogs

Phenobarbital Overdose in Dogs

Overdose will cause extreme sedation. A severe overdose is life-threatening.

7 Facts You Need to Know About this  Dog Seizure Medication:

Here are the in-a-nutshell facts you need to know about phenobarbital for treatment of idiopathic epilepsy in dogs.

  1. Effective: Phenobarbital for dogs is an effective medication that helps to control epilepsy.
  2. Realistic Expectations: Often it’s not possible to make the dog completely seizure free. The aim of an anticonvulsant medication is to hit a sweet spot where the pet isn’t groggy but the seizures greatly reduced.
  3. High Doses and Liver Damage: High doses of phenobarbital for long periods of time can cause liver damage. Rather than risk permanent liver injury, the vet will suggest adding in a second medication.
  4. Combination Therapy: Potassium bromide is often the drug of choice, to add onto phenobarbital treatment. Bromide works in a different way to phenobarbital, so it corrects the problem from a different direction.
  5. Blood Levels of  Phenobarbital: The veterinarian will run blood tests every few months. This is to check the serum concentrations of phenobarbital is at a therapeutic level. It’s also to check on the health of the liver.
  6. Twice Daily Dosing: Phenobarbital holds a steady level for around 12 hours. After this time, the serum concentration starts to fall. A rapid decrease can trigger seizures. This means phenobarbital needs to be given twice a day. The ideal dosage regime is to give the tablets exactly 12 hours apart.
  7. Initial Sedation: If your pet is starting phenobarbital for the first time, expect them to be groggy. But as the body gets used to the drug, this sedation quickly wears off. If the dog still appears drunken after 3 or 4 days, let the vet know.

And the last word is never to stop phenobarbital suddenly. If you have concerns about giving this drug to your dog, speak to your veterinarian. They can discuss the pros and cons, and if necessary suggest alternative medications like cbd oil for dogs.

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Common Questions on Phenobarbital for Dogs

What is Phenobarbital for Dogs?

How Do I Give my Dog Phenobarbital?

What is Phenobarbital for Dogs Used for?

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