Grapefruit and its juice (fresh or frozen) can either increase or, less frequently, decrease the effects of some drugs. Grapefruit contains substances that can interfere with the transformation and elimination of certain drugs when they are administered orally, resulting in serious adverse reactions.
As little as 200 mL of juice or a whole grapefruit can cause a significant increase of blood levels of certain drugs. The effects of grapefruit can last up to 3 days, sometimes even longer. Because the effects of grapefruit last a long time, they cannot be avoided by spacing medication and grapefruit apart. Drinking grapefruit juice in the morning, for example, and then taking your medication at night will not eliminate the risk of interaction.
Grapefruit interactions are highly unpredictable. Not everyone will react the same way; it depends on which drug is involved, the grapefruit itself, and how sensitive you are to these effects.
To minimize the risk of drug interaction, refrain from eating grapefruits or drinking grapefruit juice before checking with your pharmacist. Other citrus fruit may produce similar effects to grapefruit, including:
- Seville oranges (used in marmalade)
However, not all citrus fruit need to be avoided. Those listed below are considered safe:
- Sweet oranges (Navel or Valencia)
Patients treated with certain medications may have to avoid other fruits and their juices (e.g., starfruit, pomegranate). Speak to your pharmacist.
Be alert and avoid taking your medications with grapefruit before checking with your pharmacist or physician.