Grapefruit and grapefruit juice is a healthy food and drink that can cause interactions with many different drugs and affect how they interact with the body.
The most common pathway for drug metabolism so it can be inactivated and excreted is the cytochrome P450 pathway in which the enzyme, cytochrome P450 3A4 (CYP3A4) inactivates many of the drugs. As this enzyme is found in cells that line the small intestines, colon and the liver, it means that for drugs that are taken orally will have a percentage of it removed in the intestines and then the liver affecting the bioavailability of the drug. Anything that affects the activity of the cytochrome P450 3A4 enzyme may affect the amount of the drug that reaches the bloodstream.
Grapefruits produce furanocoumarins that can inhibit CYP3A4 by binding to the enzyme and inactivating it. This will lead to greater levels of a drug in the bloodstream which is metabolized via this pathway when the drug is taken orally.
Examples of common drugs that can interact with grapefuit:
Aliskiren; alprazolam; atorvastatin; carbamazepine; clarithromycin; colchicine; erythromycin; fentanyl; fexofenadine; loratadine; lovastatin; nifedipine; palbociclib; pimozide; ranolazine; sildenafil; simvastatin; vardenafil; verapamil; warfarin
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