Why is the combination of grapefruit and certain medications dangerous?

The combination of grapefruit with certain medications can be dangerous due to the interaction between substances in the fruit and the processing of medications in the body. This interaction can lead to an increased or decreased concentration of the medication in the blood, which can have serious consequences.

Cytochrome P450 3A4 (CYP3A4) is an enzyme that plays a crucial role in the breakdown of many medications. Grapefruit contains substances such as furanocoumarins that inhibit CYP3A4.

When CYP3A4 is inhibited, a larger portion of the medication can enter the bloodstream. This can lead to too high a medication concentration.

The interaction with grapefruit is particularly relevant for medications that are metabolized via CYP3A4, such as cholesterol-lowering drugs (statins) such as atorvastatin, simvastatin and rosuvastatin. This increases the risk of muscle breakdown (rhabdomyolysis) and kidney problems.

Blood pressure medication such as calcium channel blockers (e.g. amlodipine, felodipine) can cause too great a drop in blood pressure in combination with grapefruit. Anticoagulants such as coumarins, rivaroxaban or apixaban have an increased risk of bleeding.

Even a small amount can have a significant effect, depending on the sensitivity of the drug. If you are taking medications that are known to interact, it is wise to avoid grapefruit and other citrus fruits such as Seville oranges.

Author: Prof. Dr. Dirk Devroey - Latest update: 2025-01-20 - Copyright: Clinifacts 2025