Hyperammonemia in asterixis induced by carbamazepine: two case reports

Area of Science:

• Neurology
• Clinical Pharmacology

Background:

• Carbamazepine is a widely used antiepileptic and mood-stabilizing drug.
• Asterixis is a motor disorder characterized by irregular flapping movements, often associated with metabolic encephalopathies.

Observation:

• Two patients on carbamazepine therapy developed asterixis.
• Carbamazepine levels were within the therapeutic range.
• The primary laboratory finding was mild hyperammonemia.

Findings:

• Hyperammonemia and asterixis were dose-related effects of carbamazepine.
• Hepatic function remained normal in both patients.
• Discontinuation or dose reduction of carbamazepine led to the cessation of asterixis and normalization of ammonia levels.

Implications:

• Carbamazepine can induce hyperammonemia and asterixis even at therapeutic doses.
• Monitoring ammonia levels may be warranted in patients developing asterixis during carbamazepine treatment.
• This suggests a potential mechanism of carbamazepine-induced neurotoxicity independent of significant liver dysfunction.