Valproic acid therapeutic plasma level is within which range?

• A. 50-100 mcg/mL
• B. 10-20 mcg/mL
• C. 4-12 mcg/mL
• D. 10-40 mcg/mL

Answer: (A)

Valproic acid is kept in a specific blood level window to balance seizure control with toxicity risk. Because it binds to albumin and varies a lot between patients, clinicians use trough levels to guide dosing. The commonly accepted therapeutic trough range is 50 to 100 mcg/mL (which is the same as 50–100 mg/L). Levels in this window are typically effective for seizure prevention without causing major toxicity. Subtherapeutic levels (below this range) may not prevent seizures, while levels above this range increase the risk of hepatotoxicity, thrombocytopenia, and CNS side effects.