- Drug interactions: Grapefruit juice can affect drug metabolism and reduce their effects, or even worsen side effects. Grapefruit can interfere with the enzymes and transport mechanisms involved in the breakdown or absorption of medications in the intestines, causing the levels of medications in the body to be too high or too low. Avoid eating grapefruit while taking medications such as statins, calcium channel blockers, blood pressure medications, and psychotropic medications.
- High in potassium: Grapefruit contains high amounts of potassium, which means people with kidney infections should consume it with caution. Their kidneys may not be able to filter out excess potassium, which can be life-threatening for these people.
- Highly acidic: Because grapefruit is highly acidic, it may worsen heartburn and reflux symptoms in people with gastroesophageal reflux disease (GERD).
Unusually, fruits with significant health benefits can be dangerous for some people. But that’s the case with grapefruit . Grapefruit interacts with many common oral medications, including several oral cancer drugs. If you take one of the affected medicines, you may notice a warning on the bottle label or in your pharmacy's Patient Information Guide.
drug interactions
Grapefruit contains compounds called furanocoumarins, which inactivate the CYP3A4 enzyme in the intestines. This enzyme metabolizes certain oral medications, so blocking its action means more of the medication enters your bloodstream. Even small amounts of furanocoumarins can cause certain medications to reach dangerous levels in your blood.
Research reports that just 250 milliliters (about 8 ounces) of grapefruit juice can triple the concentration of the drug in the blood compared to water. Drinking the juice three times a day for five days further increased the drug concentration by as much as five times. Combining grapefruit with certain medications may cause side effects. In the worst-case scenario, grapefruit combined with some of these drugs can be fatal.
Grapefruit isn't the only thing that contains furanocoumarins. Oranges, grapefruits, limes and Seville bitter oranges (often used in orange marmalade) also contain them. Of these, grapefruit has been the most studied because eating large amounts of it can often cause reactions. Not only juice, but also fruits and peels can be problematic.
One of the most serious side effects of furanocoumarins is an irregular heartbeat called torsade de pointes, which can lead to sudden death. He noted that other potential side effects include gastrointestinal bleeding, kidney damage, breathing problems and rhabdomyolysis (a disease in which muscle tissue breaks down).
However, he said furanocoumarins affect everyone differently. Some people produce more CYP3A4 enzyme than others. Those who have more CYP3A4 in their small intestines are at greater risk of drug toxicity if they consume grapefruit. But without testing, it's impossible to predict who will be affected by grapefruit. Because the magnitude of interactions can vary widely, doctors and pharmacists recommend that anyone taking the affected medications avoid eating grapefruit and related fruits.
Grapefruit has been linked to 121 drugs on the interaction list. They range from heart and blood pressure medications to anti-anxiety medications to, increasingly, anti-cancer drugs. This interaction is drug specific, so not all drugs in the same drug class will be affected. Some common drugs that interact with furanocoumarins include:
- Certain oral anticancer drugs are called tyrosine kinase inhibitors and CDK inhibitors. Some of them include Verzenio (abemaciclib), Xalkori (crizotinib), Sprycel (dasatinib), Tarceva (erlotinib), Afinitor (everolimus), Ibrance (palbociclib), Votrient (pazopanib), Kisqali (ribociclibuni), and Sutzoent (panib).
- Blood pressure and heart medications, such as Plendil (felodipine), nifedipine, and Multaq (dronedarone).
- Certain cholesterol medications, such as Lipitor (atorvastatin), Sutra (simvastatin), and mevastatin (lovastatin).
- Some anti-anxiety medications include Valium (Valium) and BuSpar (Buspirone).
- Oral central nervous system medications and pain relievers, such as oxycodone, fentanyl, and ketamine.
Sixty percent of the drugs that interact with grapefruit juice are high-risk and may cause serious adverse reactions. Of these high-risk drugs, 27 are kinase inhibitors, oral drugs used in cancer treatment. "
The number of oral cancer drugs that interact with grapefruit has increased significantly over the past decade. These drugs treat a variety of cancers, putting an increasing number of patients at risk.
There's an important reason why grapefruit interaction warnings appear on some cancer and other drug labels. Unless your doctor advises otherwise, avoid grapefruit while taking these medications. If you are not sure whether your medications interact with grapefruit, talk to your oncologist or pharmacist.
