The number of prescription drugs that can interact with grapefruit is increasing. Grapefruit contains furanocoumrarins which are capable of blocking CYP3A4, enzymes in the liver that normally break down medications, left in the body. Without these enzymes, medication levels in the body can grow to toxic amounts. Adverse effects include sudden death, acute kidney failure, respiratory failure, gastrointestinal bleeding, bone marrow suppression, and renal toxicity. This phenomenon is dubbed the “Grapefruit-Juice Effect.”
Currently, there are more than 85 drugs that can interact with grapefruit and 43 of them produce very serious side effects. But it doesn’t stop at just grapefruits. Other citrus fruits such as Seville oranges, pomelos, and limes contain furanocoumarins. The interaction between furanocoumarins and CYP3A4 is irreversible. A normal serving of grapefruit can multiply the effects of the drug dose. Even if the grapefruit is consumed hours before taking medication, this interaction can still occur.
People older than 45 years are especially at risk because they are the prime consumers of grapefruit and also receive the most prescription drugs. Older adults also have a decreased ability to tolerate excessive drug concentrations.
Despite the wide range of drugs that can interact negatively with grapefruit, there are grapefruit-friendly prescription drugs. Always consult your doctor before ingesting medication with grapefruit in your diet. Only a small amount of grapefruit or grapefruit products is required to produce a dangerous interaction.