What is a common drug–drug interaction involving grapefruit?

• A. Grapefruit inhibits CYP3A4, increasing levels of certain drugs (e.g., some statins and calcium channel blockers).
• B. Grapefruit enhances absorption for all drugs.
• C. Grapefruit neutralizes QT-prolonging meds.
• D. Grapefruit reduces metabolism of vitamins.

Answer: (A)

Grapefruit juice can block the enzymes responsible for metabolizing many drugs as they are absorbed in the gut, mainly intestinal CYP3A4. When this enzyme is inhibited, the drugs aren’t broken down as quickly, so more of the active drug gets into the bloodstream. That raises drug levels and can increase the risk of adverse effects. This interaction is particularly important with certain statins (for example, simvastatin and atorvastatin) and some calcium channel blockers (such as felodipine and nifedipine), where higher exposure can lead to toxicity or exaggerated effects. The other statements aren’t correct because grapefruit does not universally enhance absorption for all drugs, it does not neutralize QT-prolonging medications, and it does not reduce the metabolism of vitamins. In practice, patients on these interacting medications are advised to avoid grapefruit or discuss alternatives with their clinician.