Risperidone plasma levels are reduced by carbamazepine.

Risperidone plasma levels are reduced by carbamazepine.

• A. Risperidone
• B. Quetiapine
• C. Ziprasidone
• D. Clozapine

Answer: (A)

Carbamazepine is a powerful inducer of hepatic drug‑metabolizing enzymes, especially CYP3A4. When a drug that is cleared by these enzymes is taken with carbamazepine, its plasma levels drop because the body speeds up its metabolism. Risperidone is mainly broken down by the liver via CYP2D6 to an active metabolite, 9‑hydroxyrisperidone, and to some extent by CYP3A4. Inducing these enzymes with carbamazepine speeds up risperidone metabolism, lowering the amount of risperidone (and its active metabolite) in the blood. That reduced exposure can lessen the antipsychotic effect, so clinicians might need to adjust the risperidone dose or consider an alternative when carbamazepine is added. (Other antipsychotics can be affected by enzyme induction as well, but the example here specifically notes risperidone as having reduced levels with carbamazepine.)

Carbamazepine is a powerful inducer of hepatic drug‑metabolizing enzymes, especially CYP3A4. When a drug that is cleared by these enzymes is taken with carbamazepine, its plasma levels drop because the body speeds up its metabolism.

Risperidone is mainly broken down by the liver via CYP2D6 to an active metabolite, 9‑hydroxyrisperidone, and to some extent by CYP3A4. Inducing these enzymes with carbamazepine speeds up risperidone metabolism, lowering the amount of risperidone (and its active metabolite) in the blood. That reduced exposure can lessen the antipsychotic effect, so clinicians might need to adjust the risperidone dose or consider an alternative when carbamazepine is added.

(Other antipsychotics can be affected by enzyme induction as well, but the example here specifically notes risperidone as having reduced levels with carbamazepine.)