Phenobarbital: The Best Treatment for Dog Epilepsy?

Today I want to talk to you all about one of the most common drugs used to control seizures and treat epilepsy. This drug is called phenobarbital and there are some very important things to know if your dog is suffering from seizures and taking this medication.

Is it the best treatment for dog epilepsy? Read on!


Now while epilepsy is a relatively common disease in our pet dog population, as I’ve discussed in a separate article, there are many other causes of seizures in dogs. While phenobarbital may be used to treat seizures due to any cause, it is used most commonly in the treatment of epilepsy and comes under many different brand names including epiphen and epityl.

The drug itself is also known as phenobarbitone, the two names being interchangeable.

How well does phenobarbital work?

It is a pretty effective first choice, with over 80% of epileptic dogs having their number of seizures reduced by half and about a third of dogs actually becoming seizure free, The phenobarbital in effect completely eliminating their seizures.

It’s not a drug though that can be guaranteed to have an effect. Around 15% of epileptic dogs will fail to improve at all.

So that’s how effective phenobarbital is at controlling epileptic seizures in dogs. Unfortunately, if the seizures are caused by something else, such as organ failure or a brain tumour, then the benefit of phenobarbital is much less predictable, as well as generally being significantly less effective.

Speed of action

When it comes to starting treatment, It takes 7-14 days for blood levels to stabilize and the full ability of that drug dose to control the seizures to be evaluated. It may be that a dog is started off at a higher dose to try and speed up this process, although this does increase the chance of side-effects developing. The best dosing plan for your dog is clearly something that will be assessed by your vet, and if side-effects do develop then this will need to be re-evaluated.

Side effects

So what are the potential side effects of phenobarbital in dogs?

Well to start with, sedation and wobbliness are frequently seen when treatment is started. These typically resolve within a week unless really high doses are given.

Vomiting can also be a problem, especially when first given. While phenobarbital doesn’t have to be given with food, if your dog is being sick then giving with a full meal can help prevent vomiting.

Similarly, an increased thirst, increase in urination and becoming very hungry are often seen at the start of treatment. These can persist while a dog is being given phenobarbital but will frequently become less severe or resolve completely with time.

Moving onto much less common side-effects, the big one is the potential to cause liver damage or failure. This is one of the main reasons that monitoring blood tests are carried out. These blood tests will often show a mild to moderate increase in liver enzymes which in itself is generally not an indication of liver failure. If though the levels are climbing steadily, or suddenly become very high then further testing might be needed or a drug change suggested.

Other uncommon side-effects mean that some dogs will become excitable, some will have a behavior change, and in very rare cases skin or blood cell disorders can develop.

Finally, though not a side-effect exactly, if phenobarbital is suddenly stopped then seizures are very likely. This can even be due to a single missed dose, so if you find that a dose has been forgotten it should be given at the first opportunity and the treatment plan then continued as normal when next due.

The best treatment for dog epilepsy?

So is phenobarbital appropriate for every dog with epilepsy or seizures? Well, no. As you can imagine, if a dogs liver is not working properly then it should not really be given at all. Care is also needed if a dog is dehydrated or anemic, has heart or lung disease, as well as in pregnant dogs or those that are lactating.

That said, an epileptic dog should not really be used to breed as epilepsy does have a genetic component with the potential to pass epilepsy on to their puppies. I discuss this and more in my article giving 11 vital facts about dog epilepsy.


Lastly, as I’ve already alluded to, any dog being given phenobarbital needs regular monitoring for two reasons. The first is to keep an eye on how effective the drug therapy is. In the first instance, this is to establish an effective dosing regimen at the start of treatment. To make sure that the drug is having the desired effect at controlling the epileptic seizures.

Once an effective dose has been established it is important that this is closely monitored because the body actually becomes more efficient at breaking down and eliminating the drug the longer a dog is being given it. As a result, it is possible for the level of control of a dogs epilepsy to become worse with time. Keeping a seizure diary is a great way of monitoring this and relaying this important information to your vet.

Blood testing is also really important. This will help monitor the level of phenobarbital in the blood which will help guide the need to change the dose being given or identify that high levels are already present which increases the chance of liver problems developing or indicate a need for a different treatment strategy should the seizures still be under poor control.

As well as measure phenobarbital levels, blood testing will also help keep an eye on a dogs liver enzymes as well as the number of cells within the blood and so give an early indication that some of the more rare but serious side-effects are becoming a problem.

So I hope this gives you some helpful points to consider when it comes to treating a dog with epilepsy or seizures due to another cause. If your dog is epileptic then remember that 3 in 4 owners consider their dog has a great quality of life and that, if they are well controlled, they have a life expectancy of around 12 years. Epilepsy and seizures can be very scary to witness but the outcome and prognosis may not be nearly as bad as you might fear.

Our Pets Health: because they’re family