Phenytoin (Dilantin) is one of the oldest drugs used for the treatment of epilepsy in humans. Unfortunately dogs metabolize Dilantin much faster than humans do making it extremely ineffective in treating canine epilepsy. One report states that only 2% of dogs have improved seizure control when Dilantin is used as a sole anti-seizure medication. In addition Dilantin must be given at high dosages every 8 hours which makes it an expensive alternative.
Mean Elimination Half-Life: 2 to 8 hours
Time to Reach Steady State Concentrations: 4 to 10 days
Target Serum Concentration: Unknown
Adverse Effects: Adverse effects in dogs associated with high serum levels include anorexia and vomiting, ataxia and sedation.
More serious side effects are liver disease and cancer of the gums.
Monitoring: It is important to monitor liver function when on chronic treatment with Dilantin.
Cautions and Warnings: The combined use of Phenobarbital or Primidone with Dilantin increases the risk of liver disease.
Discontinuing Therapy: Never discontinue therapy or alter the dose of this medication, without first consulting with your veterinarian.
Berendt, M, Clinical
Neurology in Small Animals-Localization, Diagnosis and Treatment
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Last Updated August 2009