Carbamazepine reduces olanzapine levels by what percent range?

• A. 10-20%
• B. 36-71%
• C. 0-5%
• D. 80-90%

Answer: (B)

Carbamazepine is a potent inducer of hepatic enzymes, especially CYP1A2 and CYP3A4. Olanzapine is metabolized by these enzymes in the liver, so when carbamazepine ramps up their activity, olanzapine is cleared faster and its plasma levels drop substantially. The typical reduction falls in a broad range around 36% to 71%, which is why this option is the best answer. Clinically, this can lessen olanzapine’s effect, so clinicians may need to monitor response and consider dose adjustments or an alternative anticonvulsant if needed. The magnitude reflects enzyme induction over days to weeks and can rebound if carbamazepine is stopped.