Phenobarbital for Dogs

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Phenobarbital for Dogs: The Golden Standard for Managing Canine Seizures

Veterinarians.org Team

By

Medically reviewed by

Ivana Crnec, DVM

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What Does Phenobarbital do to Dogs?

What Does Phenobarbital do to Dogs

Phenobarbital is an anticonvulsant, meaning it helps manage seizures in dogs. It is one of the oldest anti-seizure medications and has a proven track record of effectiveness. In veterinary medicine, it is used extra-label, meaning it is not FDA-approved for pets.

Phenobarbital is a prescription anticonvulsant drug, and its long-term use requires frequent monitoring by a veterinarian. Plus, in the USA, Phenobarbital is a controlled substance

From a pharmacology aspect, Phenobarbital belongs to the family of barbiturates. It controls and prevents seizures by stabilizing the brain’s neuron activity. Phenobarbital decreases the levels of glutamate (a neurotransmitter that triggers nerve stimulation) and increases the GABA levels (a neurotransmitter that blocks nerve impulses).    

What is Phenobarbital for Dogs Used for?

Phenobarbital (brand name Luminal) is used to control seizures and epilepsy and as a sedative. Let’s take a closer look at the different uses of Phenobarbital for dogs.  

Phenobarbital for Dog Seizures. Seizures are sudden and uncontrolled electrical outbursts in the brain. They are single events and can be triggered by toxins, brain tumors, head injuries, and low blood sugar levels. Seizures can occur in any dog. 

Phenobarbital for Dogs with Epilepsy. Epilepsy is a condition that manifests with repeated seizures. Some dog breeds (Beagles, Border Collies, Labrador Retrievers, German Shepherds) are predisposed to developing epilepsy

Phenobarbital for Dog Sedation. Because of the potent sedative effect, Phenobarbital can be used to achieve sedation and pronounced relaxation in dogs. However, in practice, there are other safer alternatives. 

What is the Most Common Side Effect of Phenobarbital for Dogs?

The most common side effect of Phenobarbital in dogs is transient sedation at the beginning of the therapy. If the sedation persists for more than a couple of days, you should ask the vet about dosage reduction. 

Other side effects of Phenobarbital for dogs include:

  • Increased thirst and urination 
  • Increased appetite and weight gain 
  • Ataxia (loss of coordination)
  • Lethargy or sleepiness 
  • Anxiety 
  • Agitation and restlessness
  • Anemia (long-term use)
  • Liver damage (long-term use).  

It should be noted that Phenobarbital may alter certain blood results of Cushing’s disease and thyroid gland tests. 

Because of the increased risk of side effects, Phenobarbital should be used with caution in:

  • Anemic and dehydrated dogs 
  • Dogs with compromised adrenal function
  • Dogs with heart and lung diseases
  • Pregnant and lactating dogs. 

Finally, Phenobarbital must not be used in:

  • Dogs sensitive to the active ingredient 
  • Dogs receiving meds with known interactions 
  • Dogs with kidney disease and/or liver disease
  • Dogs with severe breathing problems. 

Can Dogs Overdose on Phenobarbital?

Yes, dogs can overdose on Phenobarbital. Phenobarbital toxicosis manifests with ataxia, heavy sedation, recumbency (inability to stand), hypothermia (decreased body temperature), coma, and even death. If case of accidental ingestion, call the vet or Animal Poison Control Helpline immediately. A Phenobarbital overdose is an emergency.

Phenobarbital for Dogs Dosage 

Phenobarbital Dosage for Dogs

The recommended starting dose of Phenobarbital for dogs is 1.1 milligrams per pound of body weight (2.5 milligrams per kilograms) every 12 hours (twice a day). It is important to stick to the prescribed dose and dosing schedule. 

In case you forget to give your dog Phenobarbital, give it as soon as you remember. However, if it is close to the next dosing, skip the missed dose and continue with the regular schedule. Never double dose your dog to compensate as overdoses are possible. 

How Quickly Does Phenobarbital Work for Dogs?

It usually takes a couple of weeks before Phenobarbital for dogs starts working. However, there can be noticeable improvements after several doses. Phenobarbital has a long elimination half-life but needs time to achieve steady and therapeutic blood levels. 

Phenobarbital for Dogs Usage Guidelines

Phenobarbital is available in several oral forms (tablets, capsules, liquids, treat chewables, and pastes). Choose the form that is most convenient and give it with or without food. If your dog’s stomach is sensitive, it is better to give the Phenobarbital dose with food. 

Prolonged Phenobarbital use may result in physical dependence and tolerance. Because of the high risk of liver issues, make sure you visit the veterinarian for follow-ups and monitoring tests regularly (the exact frequency is something you should agree with the vet).  

In case you need to stop the Phenobarbital use, talk to your vet about gradually decreasing the dose. Taking your dog off Phenobarbital suddenly can lead to worsening of the situation and recurrent seizures

Before starting to use Phenobarbital, inform the veterinarian about any other meds, your dog is taking. Due to possible drug interactions, Phenobarbital should not be used or used cautiously in conjunction with:

  • Antihistamines (Diphenhydramine, Cetirizne)
  • Benzodiazepines and opioids (Methadone) 
  • Tricyclic antidepressants
  • Certain antibiotics (Rifampin, Doxycycline, Metronidazole, Chloramphenicol)
  • Some antifungals (Itraconazole, Griseofulvin, Ketoconazole, Voriconazole)
  • NSAID’s (Carprofen, Acetaminophen)
  • Corticosteroids (Prednisone)
  • Immunosuppressants (Cyclosporine)
  • Beta-blockers (Metoprolol) and heart meds (Quinidine)
  • Chemotherapy medications (Vincristine, Doxorubicin)
  • Anticoagulants (warfarin)
  • Other anti-seizure meds (Phenytoin, Valproic Acid).   

Finally, Phenobarbital should be stored at room temperature (59°F to 86°F), away from direct heat and light, and out-of-reach of pets and children. 

Alternatives for Phenobarbital for Dogs

Phenobarbital Alternatives for Dogs

If your dog does not respond to the Phenobarbital treatment or is showing severe side effects, the vet will suggest other anticonvulsant drugs. Here are some common alternatives for Phenobarbital for dogs.  

Potassium Bromide for Dogs. Potassium Bromide (KBr) can be used in conjunction with other anti-seizure medications or alone. It is very effective but needs time to reach therapeutic levels in the dog’s blood. At first, Potassium Bromide may cause sedation in dogs, and in some cases, it is linked with pancreatitis. 

Levetiracetam for Dogs. Levetiracetam is usually given to dogs whose seizure frequency and severity do not respond to other therapies. It can be used alone or in conjunction with other drugs. One of the main perks of Levetiracetam is that it has minimal side effects. However, it needs to be given three times per day.

Zonisamide for Dogs. Zonisamide is a newer anticonvulsant and the drug of choice for dogs manifesting severe side effects to other therapies. Zonisamide is relatively safe and does not cause hepatoxicity despite the fact it is metabolized in the liver. Zonisamide is cost-effective, especially for large and giant dog breeds

Gabapentin for Dogs. Gabapentin is an add-on medication, meaning when used in conjunction with other anticonvulsant drugs, it boosts their effects and allows using lower doses (which will also minimize their side effects). Gabapentin may cause sedation and ataxia, but they are rare, especially if the introduction is done gradually. 

Per Rectal Diazepam for Dogs. For pet parents, this may not seem like the ideal solution, but administering Diazepam rectally is very effective. Rectal Diazepam is the best option for dogs with cluster seizures (more than two seizures within a 24-hour timeframe). Dogs can be dosed with rectal Diazepam up to three times per day.

Instead of mainstream medications, you can also try some natural and holistic alternatives. The most popular natural remedy for seizures is CBD oil. Special diets (increased intake of medium-chain triglycerides) and acupuncture are also helpful additions to the management strategy. 

CBD (Cannabidiol) Oil for Dogs. CBD oil and CBD treats can be used to manage seizures and epilepsy in dogs. A groundbreaking study by the Colorado State University showed the effects of CBD for seizure control are promising. We suggest trying the Honest Paws CBD products for pets. They are made of organic full-spectrum hemp and are extra delicious. 

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  • Support sensitive skin & seasonal allergies
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Remember to talk with your vet regarding the use of Phenobarbital or its alternatives in dogs. The information in this article is educational and not a substitute for a veterinary consult. 

Sources

https://www.goodrx.com/healthcare-access/medication-education/what-are-controlled-substances

https://cvmbs.source.colostate.edu/preliminary-data-from-cbd-clinical-trials-promising/

https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.13841

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1681098/

https://journals.sagepub.com/doi/full/10.1177/104063871002200423

https://onlinelibrary.wiley.com/doi/10.1111/vec.12908