What is the therapeutic range for carbamazepine?

• A. 8-16 mcg/mL
• B. 1-3 mcg/mL
• C. 4-12 mcg/mL
• D. 20-40 mcg/mL

Answer: (C)

Therapeutic drug monitoring aims to keep a medication’s concentration in a window where it reliably prevents symptoms with acceptable side effects. For carbamazepine, the trough level at steady state is used to judge efficacy and safety. The standard therapeutic range is about 4–12 mcg/mL. Within this range, seizures are typically controlled and adverse effects are usually manageable. Levels below this range tend to be subtherapeutic and may allow seizures to continue, while levels above this range raise the risk of toxicity, causing symptoms like drowsiness, dizziness, ataxia, diplopia, and confusion. Carbamazepine also induces its own metabolism, so levels can change over time and require periodic monitoring to maintain balance.