The Side Effects of Phenobarb in Dogs

Phenobarb, short for phenobarbital, is a medication that is used to control seizures in dogs. Seizures are the result of physical manifestations of uncontrolled electrical activity in the brain. When the seizures are recurrent, they are often referred to as epileptic. According to the Pet Place website, phenobarb is often used to control epileptic seizure disorders in dogs by reducing the frequency and severity of seizures. While generally safe and effective, phenobarb can potentially cause side effects in dogs that can range in severity from mild to serious. If your dog experiences any of these side effects, contact your veterinarian immediately.

  1. Liver Damage

    • The Canine Epilepsy Guardian Angels website states that when phenobarb is used for longer than three months, it can cause liver scarring that can lead to liver damage in some dogs. Early signs of liver damage include weight loss, vomiting and diarrhea. Symptoms of advanced liver damage include jaundice, lethargy and a swollen abdomen. If the liver damage is caught early enough, there is the potential to reverse it with a liver cleansing diet, the elimination of phenobarb, and perhaps the addition of herbal supplements, including milk thistle. Late-stage liver damage, however, is often irreversible and sometimes fatal.

    Behavioral Changes

    • Dogs on phenobarb may experience changes in their behavior as a result of taking the drug. Phenobarb controls seizures by decreasing the activity of neurons in the brain. The phenobarb doesn’t only affect the specific neurons that cause seizures, it affects other neurons, as well. The behavioral side effects associated with this change in neurons include anxiety, restlessness, lethargy and depression, according to the Pet Place website. In addition, dogs can experience increased appetite and thirst, which can lead to increased urination and defecation. These side effects usually occur at the beginning of treatment and eventually go away after a brief period of time.

    Drug Interactions

    • The Canine Epilepsy Guardian Angels website says that phenobarb can cause interactions with other drugs your dog might be taking. Because phenobarb speeds up liver activity, it can cause other medications to be metabolized more rapidly, which can cause issues in taking them in conjunction with the phenobarb. Antibiotics like chloramphenicol and doxycycline should not be taken with phenobarb; heart medications, corticosteroids and antiparasitic drugs should also be avoided.