Which statement about drug interactions with antiseizure medications is true?

• A. Phenytoin induces hepatic enzymes reducing levels of oral contraceptives and many other drugs.
• B. Valproate has no significant interactions.
• C. Levetiracetam strongly inhibits liver enzymes.
• D. Gabapentin increases the clearance of all antiseizure meds.

Answer: (A)

Hepatic enzyme induction by certain antiseizure medications changes how other drugs are processed in the body. Phenytoin is a classic enzyme inducer, boosting the activity of multiple liver enzymes (such as CYP450 family and related pathways). This speeds up the metabolism of many coadministered drugs, including oral contraceptives, often reducing their levels and effectiveness. That mechanism explains why phenytoin can lower the concentrations of oral contraceptives and many other medications.

Valproate, in contrast, can interact in ways that often involve inhibition or displacement rather than induction, so claiming there are no significant interactions isn’t accurate. Levetiracetam tends to have minimal liver-enzyme interactions because it’s not a strong enzyme inhibitor or inducer, and gabapentin similarly has little effect on hepatic enzymes and does not broadly increase the clearance of other antiseizure medications.