Side Effects of Canine Phenobarbital

According to Vet Info, Phenobarbital is the most commonly prescribed medication for canine seizures. Like any medication given to your pet, a dog on Phenobarbital may have no side effects or any number of side effects. Knowing the possible side effects of the medication can help you decide if the benefits of it outweigh the risks.

  1. Short-Term Side Effects

    • Side effects are not a given for Phenobarbital. Not every dog will develop side effects and the side effects that develop may be varied and to a varying degree. Usually, when side effects do occur they appear in the first few weeks after beginning the medication or shortly after a change in dosage amount. Most side effects are temporary and will fade as your dog becomes used to the medication, according to Vet Info.

      Of these temporary symptoms, one of the more common symptoms is a sedative like effect. If this side effect affects your dog, he will likely become very lazy and act as if he has taken a sedative. Although, some dogs act as if sedated, others become very restless and cannot sit still. And with either hyperactivity or laziness, your dog may develop a condition known as ataxia. Ataxia is when your dog struggles with coordination. According to Canine Genetic Diseases, this can appear as limbs crossing over, balance issues or over-stepping with the front legs (Resource 2).

    Long Term Side Effects

    • Just as there are a number of side effects that will disappear as the medication stabilizes in your dog's system, there are a few side effects that can have a long term impact on your dog and tend to continue as long as the medication is used. Dogs on Phenobarbital often develop excessive eating and drinking. This also often leads to excessive urination as well as weight gain. Since weight gain is usually an on-going problem, Canine Epilepsy recommends limiting the excess food availability for your dog to help control it.

    Liver Damage

    • According to Vet Info, Phenobarbitals most serious side effect, even though it affects a small number of dogs, is liver disease. Liver disease can be a scary thought when it comes to treating your dog. Long term use of the medication can lead to a scarred liver that can fail. However, your vet will monitor your dog's blood levels to assure that there are no developing liver problems. Luckily, if your vet does detect a problem, it can usually be reversed or minimized by use of Milk Thistle, according to Canine Epilepsy. You can help monitor your dog by watching for signs of a problem. The symptoms of liver damage you should look for include loss of weight, especially if your dog has previously been gaining, yellowing skin known as jaundice, vomiting or darker than normal urine.