Carbamazepine therapeutic plasma level is within which range?

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

Answer: (A)

Carbamazepine has a narrow therapeutic window, so blood levels guide dosing to balance seizure control with tolerability. The typical therapeutic plasma concentration is about 4 to 12 mcg/mL. Staying within this range helps maximize efficacy while minimizing side effects; levels above this range raise the risk of toxicity, and levels well below may be ineffective. The other ranges—10-20, 50-100, or 10-40 mcg/mL—are either higher than needed or clearly toxic, so the 4-12 mcg/mL window is the best fit. Remember to measure trough levels at steady state and consider factors like liver function and drug interactions that can alter metabolism.