Signs of Phenobarbital Toxicity in Dogs

Signs of Phenobarbital Toxicity in Dogs

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Phenobarbital is a widely used drug in the treatment of epilepsy and other seizure disorders in dogs. While it is generally safe and effective when administered at the appropriate dosage, it can cause toxic reactions if the dog is exposed to excessive amounts. Recognizing the signs of phenobarbital toxicity is crucial in maintaining your pet’s health and well-being. In this article, we will explore the key signs and symptoms of phenobarbital toxicity in dogs, as well as discussing prevention and treatment options.

Understanding Phenobarbital

Phenobarbital is a barbiturate medication often prescribed by veterinarians to control seizures in dogs. It works by slowing down the activity in the brain, helping to control episodes of excessive electrical activity which lead to seizures. Unfortunately, phenobarbital can have some significant side effects, especially if the dose is too high, leading to a toxic reaction.

Recognizing the Signs of Phenobarbital Toxicity

Knowing what to look out for is essential in identifying phenobarbital toxicity at the earliest possible stage. Here are some key symptoms you should be aware of:

Ataxia (Loss of Coordination)

One of the most noticeable signs of phenobarbital toxicity in dogs is ataxia, or loss of coordination. This may manifest as an unsteady gait, clumsiness, or even an inability to stand or walk. Dogs may appear wobbly, as if they’re drunk or have difficulty with balance and coordination.


Sedation or drowsiness is another common sign of phenobarbital toxicity. If your dog seems excessively drowsy, lethargic, or unresponsive, this could indicate a problem. While some degree of sedation is a common side effect of phenobarbital use, excessive sleepiness or difficulty rousing your dog could indicate toxicity.

Another medication frequently given to dogs suffering from seizures is Gabapentin, which can also cause sedation. You can find out more from our article, You Gave Your Dog Gabapentin: Now He Can't Walk.

Increased Thirst and Urination

Phenobarbital can lead to increased thirst and urination in dogs, so a sudden change in these behaviors could indicate an issue. If your dog is drinking and urinating more than usual, or has started having accidents in the house, you should contact your vet.

Changes in Appetite and Weight

Some dogs experiencing phenobarbital toxicity may show changes in their appetite or experience sudden weight loss or gain. If you notice your dog eating more or less than usual, or see sudden changes in weight, it could be a sign of toxicity.


In severe cases of phenobarbital toxicity, dogs may develop jaundice, which is characterized by a yellowing of the skin, gums, and whites of the eyes. This indicates liver damage, which can occur as a result of long-term or high-dose phenobarbital use.

Preventing Phenobarbital Toxicity

Always adhere to the dosage instructions provided by your vet, and avoid giving your dog any other medications without first checking with your vet. It’s also important to schedule regular blood tests to monitor your dog’s phenobarbital levels and liver function.

Managing Phenobarbital Toxicity

If you suspect your dog is showing signs of phenobarbital toxicity, you should seek veterinary attention immediately. The vet will likely perform a blood test to confirm the diagnosis and assess the level of toxicity. The treatment may involve hospitalization and supportive care, including intravenous fluids and medications to control symptoms. In some cases, the vet may adjust the dosage of phenobarbital or switch to a different anti-seizure medication.


While phenobarbital can be an effective treatment for seizure disorders in dogs, it’s essential to be aware of the potential for toxicity and to know the signs to look out for. Regular veterinary check-ups and careful dosage management can help prevent toxicity, ensuring your furry friend stays healthy and seizure-free.

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