Phenobarbital for Dogs: Dosage, Side Effects, and Natural Alternatives

Medically reviewed by Nicole Wanner, DVM

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The first time you witnessed your dog having a seizure was likely a terrifying and scary experience. Whether its a full body grand mal seizure , or a localized petit mal seizure, it doesn't look pleasant. But once you’ve learned more about dog seizures, you will realize that they are not painful for your dog, though you probably still want to prevent them.

One option your vet may suggest is to put your dog on Phenobarbital.

So is it worth it to put your dog on this drug?


Phenobarbital is a generic name for a type of barbiturate drug. Barbiturate drugs have been around for many decades; they were widely used in humans in the 1960s and 1970s to treat anxiety, insomnia, and seizures.

For dogs, Phenobarbital is commonly used to treat seizure disorders such as epilepsy. It is a very effective drug and also inexpensive compared to the other drugs with the same purpose.

Phenobarbital can be given to your dog daily to prevent seizures, but can also be administered to your dog to stop seizures in progress.

Phenobarbital is also available under the brand names Luminal® and Solfoton®.


Seizures often occur when there is a change in brain activity, like when sleeping or waking up.

Phenobarbital works by reducing the neuron activity in the dog’s brain – think of it as a central nervous system depressant. At the same time, Phenobartial increases the natural brain chemical called GABA, a neurotransmitter that blocks nerve impulses.

As a result, the dog feels more tranquil and relaxed after taking Phenobarbital.


The FDA has not approved Phenobarbital for veterinary use, but it is still widely used. You must follow your vet’s dosage recommendation (usually based on the dog’s weight, severity, and frequency of the seizures) and instructions carefully.

You can only get a prescription for Phenobarbital from a DEA-licensed veterinarian since it is a controlled substance.

In general, Phenobarbital comes as a tablet to be given to your dog every 12 hours with or without food.

Missing a dose can result in your dog having seizures. Overdose can cause depression in the nervous system. Therefore it is essential to give Phenobarbital to your dog as prescribed and instructed by your vet.

Blood tests by your vet are essential every 2-6 months to monitor the level of Phenobarbital in your dog’s blood to make sure your dog is taking the proper and safe dosage.


While Phenobarbital is a relatively safe medication, side effects can occur. Side effects to watch out for include:

  • Agitation
  • Anemia
  • Anxiety
  • Increased thirst or appetite
  • Increased urination
  • Lethargy
  • Liver damage (long-term use)
  • Loss of coordination
  • Restlessness
  • Sedation
  • Weight gain

Phenobarbital can cause liver damage (such as scarring in the liver) after prolonged use (over three months). In rare cases, it can even cause liver failure, which is why frequent blood tests are necessary for your vet to monitor the liver function.


Phenobarbital is avoided or used with extreme caution in dogs suffering from:

  • Addison’s disease
  • Kidney disease
  • Respiratory problems
  • Existing liver disease

The following medications can have interactions when combined with Phenobarbital:

  • Acetaminophen
  • Opioids
  • Phenytoin
  • Benzodiazepines
  • Monoamine oxidase inhibitors
  • Carprofen (Rimadyl)
  • Rifampin

The effect of Phenobarbital can either be increased or decreased when combined with many other drugs, including Keppra for dogs.

You should always consult your vet if your dog is taking one or more medications before being put on Phenobarbital to avoid potentially harmful side effects.


The natural alternative with the most potential is CBD. The FDA recently approved a CBD drug (Epidiolex) for people with rare forms of epilepsy that are not treatable with conventional seizure medications.

A small 2019 study at Colorado State University found that CBD reduced seizures in most dogs when combined with anti-seizure medications like Phenobarbital.

The best part is that the side effects of CBD in dogs are relatively minimal even at extremely high dosages.

The Factor that will improve your dog’s chance of success with CBD are to use a product with an appropriate dose of CBD for your dog’s weight, generally above 0.45mg/lb twice a day for oils placed in the mouth, and more for CBD treats or oil that’s swallowed, as less is absorbed that way.

Relievet CBD dog oils and freeze-dried CBD treats for dogs are designed to make it safe and easy to provide an effective dose of CBD for dogs between 1 – 200lbs.

If you decide to explore CBD for your dog, we suggest you do it under the guidance of your vet. This is especially important if your dog is already on seizure medications, as they shouldn’t be stopped abruptly.


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