[Subacute encephalopathy. Idiosyncratic reaction to carbamazepine?]

Area of Science:

• Neurology
• Clinical Pharmacology

Background:

• Carbamazepine is a common antiepileptic drug used for seizure disorders.
• Phenytoin encephalopathy is a recognized adverse effect, but carbamazepine-induced encephalopathy is rarely reported.

Observation:

• An 81-year-old female developed confusion and worsening seizures despite therapeutic carbamazepine levels.
• Electroencephalogram (EEG) showed bilateral delta waves and a left-sided focus.
• Plasma sodium levels were within the normal range.

Findings:

• Carbamazepine withdrawal led to improvement in clinical symptoms and EEG abnormalities.
• The patient's presentation suggests an idiosyncratic reaction rather than dose-dependent toxicity or water intoxication.

Implications:

• This case highlights the potential for carbamazepine-induced encephalopathy as an idiosyncratic reaction.
• Clinicians should consider carbamazepine encephalopathy in patients presenting with neurological changes, even with normal drug levels.
• Further investigation into the mechanisms of idiosyncratic drug reactions is warranted.