Examples of some types of drugs that grapefruit juice can interact with are:
•drugs to lower cholesterol
•some blood pressure drugs
•some organ transplant rejection drugs
•some anti-anxiety drugs •some anti-arrhythmia drugs
While grapefruit juice does not affect all the drugs in those categories it's wise to check.
Technically what happens is many drugs are broken down in the small intestines with the help of an enzyme called CYP3A4. There are substances in grapefruit juice that block the action of the enzyme so instead of being metabolized, more of the drug enters the bloodstream and stays in the body longer. This can result in potentially dangerous levels of the drug in your body depending on the level of the enzyme, which varies from person to person, in your body.
Oddly, while grapefruit juice can cause a potentially toxic level of certain drugs it can have the opposite effect on some other drugs. Proteins in the body known as drug transporters help move a drug into cells for absorption and substances in grapefruit juice can block the action of some of the transporters. As a result, less of the drug is absorbed and it may be ineffective.
•Ask your pharmacist or other health care professional if you can have fresh grapefruit or grapefruit juice while using your medication.
•Read the Medication Guide or patient information sheet that comes with your prescription medicine to find out if it could interact with grapefruit juice.
•Read the Drug Facts label on your non-prescription medicine, which will let you know if you shouldn’t have grapefruit or other fruit juices with it.
•If you must avoid grapefruit juice with your medicine, check the label of bottles of fruit juice or drinks flavored with fruit juice to make sure they don’t contain grapefruit juice.
•Seville oranges (often used to make orange marmalade) and tangelos (a cross between tangerines and grapefruit) affect the same enzyme as grapefruit juice, so avoid these fruits if your medicine interacts with grapefruit juice.
The effects of grapefruit juice can last for over 24 hours so even if the medicine is taken only once a day grapefruit juice should still be avoided. Some examples of the most common or serious grapefruit juice drug interactions: alprazolam, amiodarone, atorvastatin carbamazepine, cilostazol, clarithromycin, colchicine, dronedarone, erythromycin, felodipine, fentanyl, fexofenadine, indinavir, loratadine, losartan, lovastatin, nilotinib, pazopanib, pimozide, ranolazine, saquinavir, sildenafil, simvastatin, tadalafil, vardenafil, verapamil.
The Drug Interaction Checker explains the mechanism of each drug interaction, the level of significance of the interaction (major, moderate or minor), and in certain cases, can provide the recommended course of action to manage the interaction. The Drug Interaction Checker will also display any interactions between your chosen drug(s) and food