Phenobarbital Killed My Dog

A seizure can be one of the most frightening experiences in your pet’s life, whether it is an isolated incident or a recurring one. It’s terrible as a pet owner because you feel helpless against this seemingly uncontrollable sickness that’s taking over your cherished companion. Some dogs may appear distant or unresponsive before collapsing on the floor. Your dog may also lose consciousness, appear to be swimming, or convulse.

To assist in reducing seizures in dogs, veterinarians can prescribe drugs such as phenobarbital. But what would you do if the medication meant to treat your dog ends up costing his life? If you just lost your pet due to phenobarbital intake, this article will give you more information about this seizure medication and highlight some of the reasons that could have contributed to the great loss.

What Is Phenobarbital?

Phenobarbital, also known as Luminal® or Barbita®, is most typically used to treat seizure disorders in dogs and cats, including epilepsy. Because of its excellent efficacy, it is considered the first-line treatment for seizures induced by epilepsy in dogs.

The FDA has cleared phenobarbital for human use. It is not currently approved by the FDA as a veterinary drug. It is, however, widely used in the veterinary sector, and vets can legally prescribe certain human medications to animals under certain conditions. Because this use is not stated on the medicine label, it is referred to as extra-label or off-label use. Your veterinarian will decide if this medication is appropriate for your pet.

The DEA classifies phenobarbital as a Schedule IV controlled drug. As a result, according to federal and state law regulations, this may affect the prescribing, dispensing, and refilling of this drug. It is also prohibited to consume, transfer, sell, or otherwise share your pet’s phenobarbital.

Brand Names and Other Names of Phenobarbital

This medication is only approved for use in humans.

Human formulations include Luminal® (Winthrop-Breon), Barbita® (Vortech), and a variety of generic medications.

There are no known veterinary formulations.

Phenobarbital Killed My Dog

Phenobarbital has the potential to be lethal to a dog in a variety of situations, the most common of which are misuse, overdose, or pre-existing health issues. Here are some scenarios in which Phenobarbital could result in the death of a dog: 

1. Accidental Overdose: An overdose can occur if a dog accidentally consumes more Phenobarbital than prescribed. Overdose can cause significant drowsiness, loss of coordination, delayed breathing, and unconsciousness. This can be lethal in extreme cases.

2. Allergic Reactions: Some dogs may experience an allergic reaction to phenobarbital, resulting in difficulty breathing, swelling of the face, tongue, or throat, hives, or other serious symptoms. Severe allergic reactions might be fatal in rare situations.

3. Liver Problems: Prolonged usage of Phenobarbital might be harmful to the liver, especially if the dog already has liver problems. Liver damage can worsen and result in liver failure, which is fatal.

4. Drug Interactions: Phenobarbital may interfere with other drugs that a dog is taking. These interactions may have negative effects or limit the effectiveness of other drugs, resulting in health issues or death.

5. Abrupt Withdrawal: If phenobarbital is abruptly stopped without proper medical supervision, it can cause rebound seizures that are more severe and difficult to control. These seizures can be life-threatening in some situations.

6. Inadequate Monitoring: Dogs receiving phenobarbital therapy must be regularly checked by a veterinarian to modify the dosage and gauge the medication’s efficacy. Failure to monitor the dog’s condition and modify the medication as needed can result in insufficient seizure control or overdosage.

It is critical to use Phenobarbital only as directed by a veterinarian and to strictly adhere to their instructions. Consult your veterinarian immediately if you detect any side effects or have any concerns about your dog’s Phenobarbital therapy. They can advise you on the proper dose, any adverse effects, and any required adjustments to guarantee your dog’s safety and well-being.

How Does Phenobarbital Work?

Natural chemical messengers in the brain communicate signals throughout the neurological system. Phenobarbital is a barbiturate drug that works by boosting particular chemical messengers in the brain to slow down and stabilize activity, reducing the risk of seizures.

What is Phenobarbital for Dogs Used for?

Phenobarbital (Luminal) is a sedative that is used to manage seizures and epilepsy. Let’s take a closer look at the various applications of Phenobarbital in dogs.  

Phenobarbital is used to treat seizures in dogs: Seizures are uncontrollable electrical discharges in the brain. Toxins, brain tumors, concussions, and low blood sugar levels can all cause these one-time episodes. Seizures can happen to any dog.

Phenobarbital is used to treat epilepsy in dogs: Epilepsy is a disorder characterized by frequent seizures. Some dog breeds (Beagles, Border Collies, Labrador Retrievers, and German Shepherds, for example) are predisposed to epilepsy.

Phenobarbital is used to sedate dogs: Phenobarbital can be used to achieve drowsiness and significant relaxation in dogs due to its powerful sedative action. In practice, though, there are other, safer options.

How Phenobarbital Works

Chemical messengers that are present in the brain naturally transmit impulses throughout the neurological system. Phenobarbital is a barbiturate drug that reduces the probability of seizures by encouraging specific chemical messengers to slow down and stabilize activity in the brain.

How Effective Is Phenobarbital?

It is a reasonable initial option, with over 80% of epileptic dogs seeing a 50% reduction in the frequency of their seizures and around a third of them actually becoming seizure-free. Phenobarbital effectively ends the dogs’ episodes of seizures.

However, it’s not a medicine whose effects can be guaranteed. About 15% of epileptic canines won’t make any improvement at all.

That is how well phenobarbital manages canine epileptic episodes. Unfortunately, the benefit of phenobarbital is far less predictable and often much less successful if the seizures are brought on by something else, such as organ failure or a brain tumor.

Speed Of Action

When it comes to beginning a course of treatment, it takes 7–14 days for blood levels to settle and an evaluation of the medicine dose’s complete capacity to control seizures. To speed up the process, a greater dose may be administered to the dog in the beginning, but this increases the likelihood that side effects would manifest. Your veterinarian will undoubtedly analyze the optimal dose schedule for your dog, and if adverse effects do occur, a new assessment will need to be made.

How Is It Given To Dogs? 

There are various types of phenobarbital. It comes in tablet, liquid, paste, and chewable forms. If no other dosage type seems to be working for your dog, you can also get phenobarbital as an injection from your vet. The precise dosage can also change depending on the weight, breed, and intensity of the seizures because it is digested differently by various breeds.

It is administered orally, every 12 hours, with or without food, in addition to the injections. Don’t give your dog two pills at once to make up for an unintentional dose missed! Simply ignore the missed dose and carry on with your regular dosing routine.

Since phenobarbital is not known to work instantly, it will likely take several doses before a dog starts to feel its effects. Phenobarbital’s full effects might not be felt for a few weeks. While your dog is taking phenobarbital, your veterinarian will probably want to keep track of their bloodwork (usually every 3-6 months for as long as the administration continues).

Phenobarbital Side Effects

Poor coordination and sedation

This is typically observed at the beginning of therapy, following dose increases, or when an additional medication, such as bromide, is added. Usually, this effect disappears after two weeks. If it doesn’t or is too much, your veterinarian may suggest that you lower the dose of phenobarbitone or switch to another medication.

Increased urination and drinking

Phenobarbitone has a diuretic effect. When receiving phenobarbitone medication, your pet must constantly have access to water because otherwise, they risk becoming dehydrated. Some animals receiving high doses may have urinated inside the home overnight or when left alone for a long time.

Increased appetite

Your pet’s appetite may increase with phenobarbitone medication, although they frequently may not need extra food.

It can be challenging to prevent weight gain. Feeding your pet a reduced-calorie meal may be beneficial so they can eat more without gaining weight.  

For example, you can replace your regular dog treats with green beans.

Liver damage

Even though this is a widely discussed issue in animals taking anti-epileptic medication, is rare. The liver, where phenobarbitone is metabolized, may become harmed during the process.

This could occur in one of two situations:

I) The animal has an idiosyncratic reaction to the medication, which is unfortunate

It is impossible to foresee this.

2) There is a history of liver illness. Therefore, blood samples are typically taken to check liver function both before commencing treatment and occasionally (often every 6–12 minutes) while receiving treatment.

3) Excessively high doses of the medication are administered over an extended period. It is not advisable to continue to administering a dose of more than 12 mg/kg/day or a serum concentration of more than 30 mg/l, or 145 mol/l.


Dogs with epilepsy are more likely to develop pancreatitis or pancreatic inflammation. Clinical indications of pancreatitis might include vomiting and anorexia, and in extreme cases, it can be fatal. There are probably several risk factors for this illness, including obesity, persistently high resting triglycerides, a high-fat diet, a propensity to scavenge, and large dosages of phenobarbitone combined with bromide.

Blood cell abnormalities

Phenobarbitone may incredibly infrequently cause issues with blood cell growth or degeneration.

Contact your veterinarian if you have any worries about your pet after receiving a phenobarbitone prescription.

Interactions With Other Drugs

When Phenobarbital was given to animals, the following medication interactions were either reported or theorized:

  • Acetaminophen
  • Monamine Oxidase Inhibitors
  • Phenytoin
  • Rifampin
  • aminophylline
  • anticoagulants 
  • antihistamines
  • beta-blockers
  • chloramphenicol
  • CNS depressants
  • corticosteroids 
  • doxycycline
  • erythromycin
  • furosemide
  • griseofulvin
  • lysodren
  • metronidazole
  • NSAIDs
  • opiate agonists
  • phenothiazine
  • phenytoin
  • quinidine
  • rifampin
  • theophylline 
  • valproic acid.

The effects of phenobarbital may be intensified by certain medications:

  • Antihistamines
  • Chloramphenicol
  • Opiates
  • Phenothiazines
  • Valproic Acid

What dogs should not take this medication?

Breeding, nursing, pregnant, or nursing animals. 

Use with great caution in animals with liver or lung disease.

Use with caution in animals who are dehydrated or anemic, or who have Addison’s, heart, or kidney problems

Alternatives for Phenobarbital for Dogs

The veterinarian will recommend different anticonvulsant medications if your dog does not react to the phenobarbital treatment or exhibits severe side effects. Here are a few popular canine phenobarbital alternatives.  

Potassium Bromide for Dogs: You can use potassium bromide (KBr) by itself or in combination with other anti-seizure drugs. Although it is quite effective, it takes some time for the dog’s blood to reach therapeutic levels. Potassium bromide initially could make dogs drowsy, and it’s occasionally associated with pancreatitis.

Levetiracetam for Dogs: Levetiracetam is typically administered to dogs whose frequency and severity of seizures do not improve with previous treatments. It may be taken alone or in combination with other medications. Levetiracetam has few adverse effects, which is one of its key advantages. It must be administered three times daily, though.

Zonisamide for Dogs: The anticonvulsant of choice for dogs exhibiting severe side effects from earlier treatments is zonisamide, a more modern medication. Despite being processed in the liver, zonisamide is generally harmless and does not have any adverse effects on the liver. Zonisamide is affordable, especially for large and giant dog breeds.

Gabapentin for Dogs: When used with other anticonvulsant medications, gabapentin enhances their efficacy and permits the use of lower doses (which will also lessen their negative effects). Sedation and ataxia are possible side effects of gabapentin, but they are uncommon, especially if it is introduced gradually.

Per Rectal Diazepam for Dogs: Although giving Diazepam rectally may not seem like the best option for pet parents, it works quite well. The most effective treatment for canines experiencing cluster seizures (more than two seizures within 24 hours) is rectal benzodiazepines. Rectal Diazepam doses for dogs can be administered up to three times daily.

CBD (Cannabidiol) Oil for Dogs: Dogs with epilepsy and seizures may benefit from CBD oil and CBD treats. Colorado State University conducted a ground-breaking study that demonstrated CBD’s potential to control seizures. 

Does My Dog Need To Be Monitored While Taking Phenobarbital?

Yes. Your dog’s blood will be periodically tested by the vet to determine its phenobarbital levels. Between 15 and 35 g/mL of phenobarbital in the blood is the optimal range. The veterinarian may adjust the phenobarbital dosage and retest your dog two weeks later if the levels come back lower or higher than this.

Red blood cell counts and the health of your dog’s liver will both be examined to look for any of the severe side effects mentioned above. When your dog first begins taking phenobarbital, blood tests will be performed more frequently. They will then be performed every six months after they are taking a consistent dose and responding well.

What Should I Do If My Dog Continues To Have Seizures While Taking Phenobarbital?

After taking phenobarbital for two weeks, if your dog’s seizures persist, call your vet right away. Seizures occurring after this could indicate an incorrect dose or the need for a different medicine for your dog. After a breakthrough seizure, your veterinarian could advise you to give your pet an additional dose, but you should only follow this advice if it is recommended by your vet. Your dog could suffer harm if you provide an excess dose on your own.

It is beneficial to keep a seizure diary where you can note the duration, symptoms, and events that happened just before and after the seizure. Think about recording your dog so you can show the vet. This extra information may aid your veterinarian in determining the best course of action for treating your dog’s seizures.

Phenobarbital Dosage for Dogs

You shouldn’t use this medicine without a prescription. Always consult your veterinarian before administering phenobarbital to your dog.

Phenobarbital for dogs should be administered twice daily at a starting dose of 1.1 milligrams per pound of body weight (2.5 milligrams per kilogram). It’s crucial to follow the dosage instructions and schedule.

Based on the results of blood tests, the dosage of phenobarbital needs to be adjusted. This is because your dog may be metabolizing phenobarbital either more quickly or more slowly than usual. The appropriate dose for your dog can be determined by a veterinarian using blood level measurements. These tests ought to be carried out:

  • Two to four weeks after starting phenobarbital
  • Two to four weeks after changing the dose
  • Three months after first starting treatment
  • Every 6 months while treatment is ongoing
  • Whenever seizure control is unsatisfactory

Phenobarbital does not cure seizures. Your veterinarian will work to lessen the frequency and intensity of seizures while minimizing unwanted effects.

How Do I Minimize Phenobarbital Side Effects in Dogs?

Use the lowest viable dose of phenobarbital that appears to be effective for your dog to reduce side effects over the long run. This is where routinely keeping an eye on your dog’s blood levels and any behavioral changes is beneficial.  

The earlier you can identify any of these warning signs or symptoms, the greater your chances are of successfully treating your dog while minimizing unpleasant side effects and associated health issues.

When Should I Stop Using Phenobarbital in Dogs?

The timing of your dog’s phenobarbital withdrawal is entirely up to you. Your dog might be a good candidate to stop taking phenobarbital if he has been seizure-free for at least a year or two.

This is especially true if your dog is experiencing severe side effects that are impairing his quality of life or if you have reason to believe your dog may be suffering from liver damage. It is better to quit taking the medication before any liver damage gets worse.

However, keep in mind that phenobarbital shouldn’t ever be stopped abruptly because doing so could result in more seizures. Your dog may still have seizures during the withdrawal phase even if you gradually wean them off phenobarbital under the vet’s guidance. 

Does phenobarbital for dogs cause aggression?

Phenobarbital has the rare ability to make certain dogs aggressive and hyperactive. When this occurs, see your veterinarian about phenobarbital substitutes or a phenobarbital dosage adjustment.

Tips For Managing Your Dog’s Epilepsy With Phenobarbital

  1. Find the ideal phenobarbital dosage for your dog by consulting with your vet. In the event that your dog’s weight changes or if additional medications are used, the phenobarbital dosage might need to be changed.
  2. Never miss a dosage and be consistent in your dosing schedule.
  3. Avoid administering phenobarbital right after a full meal.
  4. Give the missed dose as soon as you remember it if you do. Skip the missed dose and carry on with the regular dosing plan if the next dose is almost due. Never provide two doses at once.
  5. Make sure your veterinarian has prescribed a loading dose of phenobarbital for your dog when you first start it, but in moderate increments to reduce the likelihood of respiratory depression.

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