Which medication is contraindicated due to its interaction with carbamazepine?

Grapefruit juice is contraindicated with carbamazepine because it can significantly affect the metabolism of the medication in the liver. Carbamazepine is metabolized by the cytochrome P450 system, specifically CYP3A4. Grapefruit juice inhibits this enzyme, leading to increased levels of carbamazepine in the bloodstream. This can heighten the risk of side effects and toxicity, making it crucial for patients taking carbamazepine to avoid grapefruit juice to maintain safe and effective drug levels.

In contrast, amiodarone, vancomycin, and digoxin do not have significant interactions with carbamazepine that would warrant a contraindication. While these medications can have their own interactions and considerations, grapefruit juice's direct and pronounced effect on carbamazepine metabolism is a specific concern that necessitates avoiding its consumption for individuals on carbamazepine therapy.