Phenobarbital for Cats: A First-Choice Treatment for Managing Epilepsy and Seizures
Key takeaways:
Phenobarbital is an effective treatment for chronic seizures in cats.
Phenobarbital can cause too much sedation in cats, with slow and ineffective breathing being a major risk of the medication.
Phenobarbital has the potential to interact with many other cat medications, including anesthetics and sedatives, antibiotics, and behavioral and pain medications.
Table of contents
While epilepsy and chronic seizures are not as common in cats as they are in dogs, feline family members can still have these conditions. Cats who commonly experience seizures need to take medication for the rest of their lives to manage their seizures.
Phenobarbital is a first-choice medication for the long-term management of seizures in cats. Learn how phenobarbital works, what its potential side effects are, and about its interactions with other medications.
Phenobarbital for cats at a glance
Common names | Phenobarbital |
What it treats | Epilepsy and seizures |
How it comes (forms) | Tablets, compounded transdermal gel or lotion, compounded oral suspension, and injectable |
Dosage | Depends on a cat’s weight and is determined by a veterinarian |
Common side effects | Sedation, lethargy, clumsy gait, appetite changes, and increased urination and thirst |
Average cost |
What is phenobarbital for cats, and how does it work?
Phenobarbital is primarily used to reduce the frequency of seizures in cats who have conditions such as epilepsy and brain tumors. It’s considered a first-choice treatment for managing seizures in cats.
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Phenobarbital belongs to a class of medications called barbiturates. The medication depresses the central nervous system (brain and spinal cord). As a result, it reduces seizure activity.
Phenobarbital is not FDA approved for use in cats. This means using the medication to treat cats is considered extra-label. It’s common for human medications to be prescribed extra-label, or off-label, to cats.
Phenobarbital is also a controlled substance in the U.S., which means there may be extra restrictions when it’s prescribed.
What is the typical dosage of phenobarbital for cats, and how is it given?
Dosages of phenobarbital for cats with epilepsy vary. The typical starting dosage is 2 mg to 2.5 mg per kilogram of body weight every 12 hours. This usually means either ½ or 1 whole 15 mg tablet by mouth every 12 hours.
More studies are needed to verify that transdermal phenobarbital applied as a gel or lotion inside of the ear flap is effective. But transdermal phenobarbital can be compounded for pet owners who struggle to give oral medications to their cat. When this method is used, the dosage is 9 mg per kilogram of body weight applied inside the ear flap every 12 hours.
Phenobarbital can also be compounded into an oral liquid for cats. The typical starting dosage is the same as with tablets.
Cat seizures: If your cat has seizures, there are a number of things that are important to know. This article walks you through how to help your feline friend.
Catnip and seizures: Most cats love catnip. But if your cat has seizures, be careful not to give them too much because it can trigger a seizure.
Toxic foods: Don’t let your cat get into these human foods, because they’re toxic to feline friends and many can cause seizures.
In veterinary clinics, phenobarbital may be used with benzodiazepines to control active seizures. In these cases, the medication is usually given as an injection.
What are the common side effects of phenobarbital in cats?
Common side effects of phenobarbital in cats include:
Sedation or lethargy
Clumsy gait
Changes to appetite (increased or decreased appetite)
Increased thirst and urination
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Less commonly, cats can develop excessive itchiness on their face when taking phenobarbital.
Your veterinarian will likely recommend regular blood tests for your cat while they’re taking phenobarbital. This will help monitor for other potential side effects.
What are the most serious risks of phenobarbital for cats?
One of the more serious risks of phenobarbital for cats is excessive sedation that can result in respiratory depression (slow or difficult breathing).
In rare cases, cats taking phenobarbital can develop an immune system reaction to the medication that causes low counts of red blood cells, white blood cells, or platelets.
Does phenobarbital interact with any other cat medications?
Phenobarbital has the potential to interact with the following medications used in cats:
Alpha-2 agonists, such as dexmedetomidine
Antibiotics like clindamycin and doxycycline
Antifungals like itraconazole
Antihistamines, such as diphenhydramine
Benzodiazepines, such as diazepam and midazolam
Opioids, such as buprenorphine
If your cat takes one of these medications, your veterinarian will weigh the risks versus the benefits before prescribing them phenobarbital. Be sure to let your veterinarian know about all of the medications your cat is taking.
What should you do if your cat misses a dose of phenobarbital?
If your cat misses a dose of phenobarbital, it is best to speak with your veterinarian about next steps.
Your veterinarian will likely tell you to go ahead and give your cat the medication if it hasn’t been too long since the missed dose. If it’s nearly time for your cat’s next dose, they may have you skip the missed one and continue with the normal schedule.
Do not give your cat a double dose of phenobarbital, as this can increase the risk of side effects. If your cat experiences a seizure because of a missed dose, contact your veterinarian as soon as possible.
The bottom line
Phenobarbital is considered a first-choice treatment option for most cats with epilepsy. The medication does have the potential to cause excessive sedation or a clumsy gait. These side effects are more likely when phenobarbital is used in combination with certain anti-seizure medications, anesthetics, sedatives, and pain medications.
If your cat is having seizures, speak with your veterinarian about whether phenobarbital is a good option for them.
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References
Charalambous, M., et al. (2018). Systematic review of antiepileptic drugs' safety and effectiveness in feline epilepsy. BMC Veterinary Research.
Charalambous, M., et al. (2023). ACVIM consensus statement on the management of status epilepticus and cluster seizures in dogs and cats. Journal of Veterinary Internal Medicine.
Dohány, A., et al. (2023). A retrospective evaluation of phenobarbital-induced hematologic changes in 69 cats. Veterinary Clinical Pathology.
Drug Enforcement Administration. (2020). Barbiturates. U.S. Department of Justice.
Gasper, J. A. D., et al. (2014). Therapeutic serum phenobarbital concentrations obtained using chronic transdermal administration of phenobarbital in healthy cats. Journal of Feline Medicine and Surgery.
Palus, V., et al. (2013). Seizuring cat: What to ask, what to do? Companion Animal.
Quesnel, A. (2001). Antileptic drug therapy in dogs and cats—an update. World Small Animal Veterinary Association World Congress Proceedings.
