Carbamazepine reduces risperidone by what percentage?

Carbamazepine reduces risperidone by what percentage?

• A. 20%
• B. 50%
• C. 5%
• D. 10%

Answer: (B)

Carbamazepine acts as a strong inducer of hepatic drug-metabolizing enzymes. By turning up the activity of these enzymes, it speeds the metabolism of drugs that are substrates, lowering their blood levels. Risperidone is cleared through the liver, mainly via CYP450 pathways, so when carbamazepine is added, risperidone exposure typically drops by about half. Clinically, this can reduce antipsychotic effect unless the risperidone dose is adjusted or another regimen is used, so monitoring response and considering dose changes or alternative therapy is important.

Carbamazepine acts as a strong inducer of hepatic drug-metabolizing enzymes. By turning up the activity of these enzymes, it speeds the metabolism of drugs that are substrates, lowering their blood levels. Risperidone is cleared through the liver, mainly via CYP450 pathways, so when carbamazepine is added, risperidone exposure typically drops by about half. Clinically, this can reduce antipsychotic effect unless the risperidone dose is adjusted or another regimen is used, so monitoring response and considering dose changes or alternative therapy is important.