Phenobarbital for Dogs

PetMD’s medications content is written and reviewed by veterinary professionals to answer common questions about how medications work, their side effects, and what species they are prescribed for. This content should not replace advice from your veterinarian. 

What Is Phenobarbital Used for in Dogs?

Phenobarbital is used to treat seizures in dogs.  

It is available as Fidoquel-CA1 tablets for dogs, as well as generic formulations for humans including a tablet, liquid, paste, or injection.  

Phenobarbital is commonly prescribed to dogs diagnosed with:  

• Epilepsy 

• Brain tumors 

• Some toxins 

Phenobarbital may be used on its own or in combination with other anti-seizure medications. 

Is Phenobarbital FDA-Approved for Dogs? 

Fidoquel-CA1 has been conditionally approved by the FDA to be reasonably safe and effective in treating epilepsy in dogs. Its full approval by the FDA is pending more robust post-marketing data to further prove its safety and effectiveness. 

Fidoquel-CA1 contains phenobarbital that is specifically formulated for dogs.  

Human generic phenobarbital is currently not FDA-approved for use in dogs. However, it is commonly used in veterinary medicine, and veterinarians can legally prescribe certain human drugs for animals in specific circumstances. This is known as extra-label or off-label use because this use is not described on the drug label. 

Speak with your veterinarian about whether phenobarbital is right for your pet. 

Phenobarbital is classified as a DEA Schedule IV controlled substance. As such, this may affect the prescribing, dispensing, and refilling of this medication due to requirements under federal and state law. Likewise, it is illegal to consume, transfer, sell, or otherwise give away your pet’s phenobarbital.  

Compounded Phenobarbital 

In certain circumstances, your veterinarian may recommend a compounded formulation of phenobarbital. 

Compounded medications may be prescribed if there’s a specific reason your pet’s health can’t be managed by an FDA-approved drug, such as if:  

• Your pet has trouble taking the commercially available form  

• The required dosage strength is not available  

• The pet is allergic to an ingredient in the FDA-approved medication 

Compounded medications are not FDA-approved. They are prepared by a veterinarian or licensed pharmacist on an individual basis to meet a pet’s specific needs. 

Phenobarbital Considerations for Dogs

Fidoquel-CA1 should not be used in animals with a history of hypersensitivity to phenobarbital. Dogs with decreased liver function may be predisposed to phenobarbital toxicosis.  

Do not use in pregnant or lactating dogs. 

The safe use of Fidoquel-CA1 in neonates and young dogs has not been established. 

The safe use of Fidoquel-CA1 has not been evaluated in dogs who are intended for breeding or who are pregnant or lactating. 

If your veterinarian recommends discontinuing this medication, follow their guidance carefully when tapering your pet off this medication. 

How Does Phenobarbital Work in Dogs?

Your pet’s brain uses natural chemical messengers to send signals throughout the nervous system.  

Phenobarbital is a barbiturate medication that helps slow down some of these signals. This helps stabilize activity in the brain, lowering the likelihood of seizures. 

How Do You Give Phenobarbital to Dogs?

Follow the directions on the drug label or as provided by your veterinarian. 

• Fidoquel-CA1 is given twice daily (every 12 hours) with food. 

• Give phenobarbital at the same time every day, as recommended by your veterinarian. 

• If your pet takes a human formulation of phenobarbital, you may give it with or without food, but consider giving it with food to help reduce the risk of digestive upset. 

• Follow your veterinarian’s guidance closely when discontinuing this medication to safely wean your pet off it.  

• Use dog pill pockets or a pill dispenser if your dog has trouble taking tablets, which can make giving medication easier and less stressful. 

What Happens If You Miss a Dose of Phenobarbital? 

Speak with your veterinarian about what to do if a dose is missed.  

Generally, your vet may instruct you to give it when you remember, or if it’s almost time for your dog’s next dose, to skip the missed dose and resume your normal dosing schedule. 

Do not give extra or double doses. 

What Are the Side Effects of Phenobarbital in Dogs?

Fatigue is very common in dogs when they first start taking phenobarbital as their bodies adjust. If your dog is severely lethargic, inform your veterinarian immediately.  

Other side effects include: 

• ​​​Increased appetite​ ​​​ 

• ​​​Increased thirst​ and ​urination​ ​​​ 

• ​​​​Weight gain ​​     ​​​ 

• ​​​Vomiting​ ​​​​​ 

• ​​Diarrhea​ 

• ​​​​Agitation​​​ 

• Loss of coordination 

Human Side Effects 

Humans should never take medication prescribed for pets, and pets should not be given medication prescribed for humans. Dosages often differ significantly. 

Women who are pregnant or may become pregnant should handle and administer Fidoquel-CA1 with caution. 

In case of accidental ingestion, skin reaction, or eye exposure, contact a physician immediately. If accidental eye contact or mucous membrane exposure occurs, rinse the exposed area thoroughly. 

You should wash skin exposed to the drug, including washing your hands thoroughly after contact. 

If you accidentally ingest a pet medication, seek medical attention or call Poison Control at 800-222-1222.  

Monitoring Your Pet 

Your veterinarian will recommend specific monitoring and routine blood testing while your dog is on this medication, depending on your dog’s individual needs, other medications that may be prescribed, and/or the issue that initially caused your dog to be placed on this medication.  

When Should You Call Your Veterinarian? 

Call your veterinarian if you see any of the following, or if you have additional questions or concerns about the use of phenobarbital: 

• Severe side effects occur  

• Your pet’s condition worsens or does not improve  

• You suspect an overdose 

What Happens If a Pet Overdoses on Phenobarbital?

Overdoses of phenobarbital can be life-threatening.  

Symptoms of an overdose may include:  

• Lack of appetite 

• Grogginess  

• Decreased energy (lethargy) 

• Low blood pressure 

• Low or high heart rate 

• Low body temperature 

• Decreased breathing rate 

• Blue gums 

• Coma 

If you suspect an overdose, seek emergency veterinary care or contact an animal poison control center. Consultation fees may apply. 

• Pet Poison Helpline: 855-764-7661 

• ASPCA Animal Poison Control: 888-426-4435 

How Should Phenobarbital Be Stored for Dogs?

Keep the following storage tips in mind for this medication:  

• The ideal storage temperature for Fidoquel-CA1 is 77 F (25 C) with temperatures between 59–86 F (15–30 C) permitted. 

• Store human phenobarbital tablets at controlled room temperature between 68–77 F (20–25 C).  

• Store human liquid phenobarbital at controlled room temperature between 59–86 F (15–30 C), and keep the container tightly closed to protect it from moisture and light.  

• Check the prescription label to confirm storage instructions. 

• Compounded medications should be stored according to the compounding pharmacy’s label. 

• Keep this medication out of reach of children and pets.