carbamazepine and fluoxetine

Pharmacokinetic interaction: fluoxetine inhibits CYP3A4, the cytochrome P450 isoenzyme responsible for carbamazepine metabolism, leading to elevated carbamazepine plasma concentrations. Carbamazepine induces CYP3A4, which may enhance fluoxetine metabolism and reduce its plasma levels.

Elevated carbamazepine levels may cause signs of toxicity such as dizziness, ataxia, diplopia, confusion, or seizures. Reduced fluoxetine levels may decrease antidepressant efficacy and risk relapse of depression.

Monitor carbamazepine plasma concentrations and clinical signs of toxicity when starting, stopping, or changing the dose of fluoxetine. Adjust the carbamazepine dose accordingly. Monitor for signs of reduced fluoxetine efficacy and consider alternative antidepressants with less enzyme inhibition if appropriate.

Well established via multiple case reports and pharmacokinetic studies. The interaction is consistent with known enzyme inhibition and induction profiles.