Compromised hepatic function in dogs treated with anticonvulsant drugs

Area of Science:

• Veterinary Medicine
• Toxicology
• Pharmacology

Background:

• Anticonvulsant drugs like primidone and phenytoin are commonly used in dogs.
• Long-term administration of these drugs may affect hepatic function.
• Previous studies on the hepatotoxicity of these drugs in dogs are limited.

Purpose of the Study:

• To evaluate the effects of long-term primidone, phenytoin, or combination anticonvulsant therapy on hepatic function in dogs.
• To identify specific liver enzymes and tests that are sensitive indicators of drug-induced hepatic changes.
• To correlate drug dosage with observed alterations in liver function.

Main Methods:

• Hepatic function tests were performed on 48 dogs receiving primidone, phenytoin, or a combination for at least 6 months.
• Dogs were assessed for clinical signs of illness, with 44 considered healthy at the time of testing.
• Statistical analysis was used to correlate drug dosage with specific biochemical parameters.

Main Results:

• Abnormal liver function tests were most frequent in dogs receiving primidone alone or in combination therapy.
• Elevated alanine transaminase (ALT) and alkaline phosphatase (ALP) activities, and abnormal sulfobromophthalein (BSP) excretion were common findings.
• Significant positive correlations were observed between primidone dosage and ALT activity, and phenytoin dosage and ALP activity.
• Four dogs exhibited signs of hepatic failure, with cirrhosis confirmed in three at necropsy.

Conclusions:

• Long-term anticonvulsant therapy in dogs frequently results in abnormal hepatic biochemical test results.
• Severe hepatic injury, such as cirrhosis, is less common but can occur.
• Monitoring of liver function is advisable in dogs receiving long-term anticonvulsant medications.