Anticonvulsants Overview for Veterinary Medicine

Anticonvulsants Overview

• Anticonvulsants are drugs used to control seizures in animals.
• Epilepsy is a brain disorder that leads to recurring seizures.
• Seizures, fits, and convulsions are synonyms for abnormal brain activity marked by sudden, uncontrolled electrical discharges.

Types of Anticonvulsants

• Phenobarbital:

  • Drug of choice for dogs and cats with seizures.
  • Effective in 60-80% of epileptic dogs when maintained within the therapeutic range (15-45 mcg/mL).
  • Depresses the motor centers of the cerebral cortex, but doesn't prevent seizure spread.
  • IV or oral administration; onset 12 hours after oral administration.

• Phenytoin:

  • Also known as diphenylhydantoin.
  • Depresses motor centers.
  • Inhibits seizure spread to adjacent neural tissues.
  • Not a general anticonvulsant like phenobarbital.
  • Poor absorption from the canine gut; given orally or intravenously.

• Primidone:

  • No hypnotic effect when used as an anticonvulsant for dogs.
  • Toxic to cats.
  • Metabolized into phenobarbital and phenylethylmalonamide, products with anticonvulsant effects.
  • Common side effects include hepatotoxicity, polyphagia, polydipsia, sedation, and behavioral changes.

• Diazepam:

  • A benzodiazepine.
  • Used primarily to control status epilepticus (severe prolonged seizures).
  • Not recommended for long-term maintenance therapy.
  • Effective in cats but not typically used in dogs.

• Potassium Bromide (KBr):

  • Effective in addition to phenobarbital, especially for clusters of seizures.
  • Often mixed by a pharmacist due to unavailability in pharmaceutical grade.
  • Can be absorbed through the skin and is toxic to humans.

• Clonazepam:

  • A broad-spectrum anticonvulsant.
  • Can be used with other anti-epileptic drugs.
  • Causes drowsiness and ataxia (loss of balance) in a dose-dependent manner.

• Valproic Acid:

  • Also a broad-spectrum anticonvulsant.
  • Absorbed rapidly.
  • Can displace bound phenytoin or phenobarbital, and metabolizes into non-anticonvulsant products.
  • Has a relatively short half-life.