Fruits that interfere with CYP3A4 (cytochrome P450 enzyme) in intestinal epithelial cells:
(1) grapefruit
(2) Seville oranges
(3) pomelos
The inhibition is irreversible so it may take time for drug metabolism to return to normal.
Recommendations for grapefruit and other fruits affecting CYP3A4 (Medical Letter):
(1) Avoid these fruits and their juices if taking a drug that requires careful maintenance of serum levels (amiodarone, carbamazepine, cyclosporine, sirolimus, tacrolimus).
(2) Limit daily intake to one 8 ounce glass or one half of a grapefruit if taking other drugs metabolized by CYP3A4, including benzodiazepines, budesonide, buspirone, dextromethorphan, etoposide, felodipine, fluvoxamine, itraconazole, lovastatin, nifedipine, nimodipine, nisoldipine, praziquantel, quinidine, sildenafil, simvastatin, verapamil.
Cranberry juice may interfere with metabolism of warfarin, resulting in over-anticoagulation and hemorrhage. The mechanism is uncertain but may involve inhibition of CYP2C9. A person taking warfarin should limit the intake of cranberry juice.
Fruits that do not interfere with cytochrome P450 enzymes:
(1) sweet oranges (and regular orange juice)
(2) tangerines
These can be taken without concern for drug accumulation.
