Lesson of the month 1: Sodium valproate-induced encephalopathy

Area of Science:

• Neurology
• Clinical Pharmacology

Background:

• Sodium valproate is a common antiepileptic drug.
• Polypharmacy is frequent in patients with epilepsy.
• Hyperammonemia can cause encephalopathy.

Observation:

• A 69-year-old man presented with sudden reduced consciousness (Glasgow Coma Scale score of 6).
• Initial investigations revealed normal brain imaging and blood tests, except for elevated plasma ammonia.
• The patient had a history of epilepsy, hypertension, and colitis, and was on multiple antiepileptic medications, including sodium valproate.

Findings:

• Discontinuation of sodium valproate and administration of naloxone led to gradual improvement in the patient's responsiveness and ammonia levels.
• The patient was also treated with ciprofloxacin for a urinary tract infection and demeclocycline for syndrome of inappropriate antidiuretic hormone secretion.
• Long-term sodium valproate use is associated with low carnitine levels, which can precipitate hyperammonemia and encephalopathy, particularly in polypharmacy settings.

Implications:

• This case underscores the importance of a thorough drug history in diagnosing altered mental status.
• Awareness of rare but serious adverse effects of medications like sodium valproate is crucial for clinicians.
• Identifying and managing drug-induced hyperammonemia is vital for patient recovery.