Controlling Canine Seizures with Primidone

Primidone is an anticonvulsant pharmaceutical drug sometimes used to help control canine seizures. Often characterized as involuntary muscle movements or behaviors, seizures are caused by surges of electrical activity in the brain.

They are generally symptoms of underlying conditions, like epilepsy, and may affect dogs of nearly any age or breed. Primidone was once commonly used to treat seizures in people and is now FDA-approved by for use by veterinarians to manage canine seizures. Understanding how Primidone works and learning about its side effects and guidelines for safe use may help owners select the right option for treating their pet's seizures.

How Does Primidone Work?

Primidone helps control the electrical activity in the brain that is responsible for seizures. The main metabolic products of the drug are phenobarbital and phenylethylmalonamide (PEMA), both of which are known to have anticonvulsant effects. Primidone works by blocking the sodium channels of cell membranes. This action helps prevent neurons, or nerve cells, from the repetitive firing action that contributes to seizures. Primidone may be prescribed by veterinarians for the long-term management of seizures caused by primary epilepsy, which is caused by inherited or genetic factors, and secondary epilepsy, which is associated with an underlying illness, infection, poisoning, injury, nutritional condition, or other disorder.

The drug may be prescribed for the treatment of generalized (tonic clonic/grand mal) seizures, marked by signs like rapid movement of limbs, chewing, pupil dilation, salivation and loss bowel or bladder control. Primidone may also be to manage petite mal or absence seizures which include periods of brief unconsciousness. In addition, the drug may be given to help manage partial seizures that effect one side of a dog's body.

Primidone Side Effects

Since Primidone is metabolized in the liver, some animal care experts caution against liver damage in dogs, particularly those taking the drug over an extended period. Dog owners should consider seeking medical care if side effects involving the liver, like yellowing skin, excessive itchiness and easy bruising, are observed. Allergic reactions to Primidone may also require immediate medical attention. Such a reaction may be characterized by:

  • Swelling of the lips, face or tongue.
  • Closing of the throat marked by a difficulty in breathing.
  • Hives.
  • Fever.
  • Increased seizure activity.

Other potential side effects associated with Primidone include:

  • Dizziness.
  • Nausea or vomiting.
  • Poor coordination.
  • Drowsiness.
  • Blurred vision.
  • Irregular eye movements.

Guidelines for Use

Primidone is typically available by prescription in the US in generic form as small 50 or 250 mg white or tan round tablets. The drug is also sold under the brand names Mysoline (Athena Neuroscience) and Neurosyn (Boehringer Ingleheim). Often sold per tablet, Primidone is designed for regular, daily use. A veterinarian will recommend the amount and frequency of dose based on the individual dog and its medical history.

Primidone is typically not recommended for dogs that are pregnant or nursing. Because of its potential effects on the liver, it is not intended for dogs with a history of liver damage. Animals undergoing long-term Primidone treatment are usually screened regularly for any signs of liver damage. Caution should also be used when considering Primidone in dogs with known histories of anemia, or certain heart, kidney or lung conditions. Drug interaction may also occur in combination with Primidone, so owners are advised to notify veterinarians if their dogs are taking other medications, particularly NSAIDs, narcotics or corticosteroids.