Severe Hyponatremia Due to Valproic Acid Toxicity

Area of Science:

• Clinical Toxicology
• Nephrology
• Endocrinology

Background:

• Hyponatremia is a common clinical condition with significant morbidity.
• Valproic acid (VPA) is an anticonvulsant and mood-stabilizing drug with known potential toxic effects.
• Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH) is a frequent cause of hyponatremia.

Observation:

• A 54-year-old woman presented with somnolence after a valproic acid overdose (7,500 mg).
• She exhibited profound hyponatremia with a serum sodium level of 99 mEq/L, low plasma osmolality, and high urine osmolality.
• No other precipitating factors for hyponatremia were identified.

Findings:

• Valproic acid overdose was identified as the cause of acute-on-chronic hyponatremia, consistent with SIADH.
• Discontinuation of valproic acid led to a gradual increase in serum sodium levels and improvement in mental status.
• The patient's serum sodium normalized to 135 mEq/L within 72 hours without neurological sequelae.

Implications:

• This case underscores a rare but severe adverse effect of valproic acid toxicity.
• Clinicians should consider valproic acid-induced SIADH in patients presenting with hyponatremia, especially following overdose or in chronic users.
• Prompt recognition and management are crucial to prevent potentially tragic outcomes.