Although citrus fruits are reliable dietary sources, many patients are concerned about the potential for grapefruit-drug interactions. You may be given a prescription medicine with a warning label attached recommending that you avoid grapefruit or grapefruit juice while taking the medication.Blood pressure lowering medicationsand grapefruit, for example, can cause side effects, but how and why do they even occur? In this article we will try to answer this question and provide you with a list of medications that are not compatible with grapefruit.
Effects of grapefruit grapefruit and medications
Drugs are processed in the liver and small intestine by a special group of proteins. These are known as cytochrome P450 (CYP). The CYPs break down drugs, lowering the blood levels of many of them. Grapefruit and medications, as well as drug interactions with some of its close relatives such as oranges, grapefruits and Seville minneola, contain a class of chemicals called furanocoumarins. These ingredients disrupt the normal function of cytochromes. In fact, studies show that they increase blood levels of over 85 medications. This means that grapefruit can increase the side effects of these medications. This happens because this citrus fruit slows down the process that normally breaks down drugs in the intestines and liver.
Interactions with grapefruit can therefore occur with common and important medications. This happens, for example, with drugs that lower cholesterol, treat high blood pressure or even with cancer drugs. The juice influences the way drugs are changed (metabolized) in the body for eventual excretion. This can change the amount of medication in the blood and lead to increased side effects or less effectiveness of the drug. New medications are approved frequently, so it's wise to research your interactions with grapefruit juice. Contact your pharmacist or doctor to find out about any possible interactions. Examples of common medications that interact with grapefruit juice,are cholesterol medicationssuch as atorvastatin, lovastatin, simvastatin, felodipine and other calcium channel blockers, clarithromycin (Biaxin) and loratadine (Claritin). Doctors report that some immunosuppressants cause kidney damage. Certain painkillers can make breathing difficult if you take them with grapefruit juice.
Grapefruit drug interaction
Drugs or toxins are normally broken down so that the body can eliminate them. Grapefruit or grapefruit juice can alter enzymes in the body and affect how medicines interact with the organism before it eliminates them. Grapefruit juice reduces the activity of cytochrome P450 3A4 (CYP3A4) enzymes, which are responsible for breaking down many drugs and toxins. This happens because the citrus fruit contains compounds known as furanocoumarins, which block CYP3A4 enzymes. When grapefruit juice is consumed, the ability of the enzyme to break down the drug for elimination is reduced. This causes blood levels of the drug to rise, leading to a risk of new or worsened side effects. A whole fruit or 200 milliliters of grapefruit juice can block the CYP3A4 enzymes and lead to toxic blood levels of the drug. A grapefruit interaction is not common with all medications. Your doctor may choose an alternative medication.
Side effects may vary depending on the interacting medication and possible side effects. These can range from abnormal heart rhythms, stomach bleeding and muscle pain to muscle breakdown, kidney damage, low blood pressure, difficulty breathing and dizziness. Other reactions may also occur. However, this depends on the drug and the levels of the drug in the blood. If you are aware of a possible interaction with grapefruit, you should ask your doctor to describe the possible side effects to learn how to recognize them. Taking medication at any time other than while consuming grapefruit juice will not prevent the interaction. The effects of grapefruit juice on certain medications can last for over 24 hours. Even if you are taking a medicine that is administered only once a day, you should avoid the combination of grapefruit and medication throughout the entire treatment period. Therefore, follow the instructions on the package leaflet for each individual medication or ask your doctor.
Grapefruit and medications for infections or antibiotics
These anti-infection drugs, known as antimicrobials, differ greatly in their effects and how they are broken down in the body. Although antimicrobials are one of the most diverse categories of medications, there are only a few of them with known important interactions with grapefruit, such as erythromycin, rilpivirine and related HIV drugs, primaquine and related antimalarial drugs such as albendazole. Erythromycin is used to treat various types of bacterial infections. A study that compared grapefruit juice with water in patients taking erythromycin showed that the juice increased blood levels of the drug by 84%. Excessive amounts of this medication may disrupt heart rhythm.
In addition to antimalarial drugs, grapefruit also increases levels of the HIV drugs rilpivirine and maraviroc. This can affect heart rhythm or function. Because antimicrobials are typically only taken for a limited time, it may be easiest to simply avoid grapefruit while taking these medications. Alternatives: Clarithromycin is a drug in the same class as erythromycin that does not interact with grapefruit. Doxycycline is both an antibiotic and an antimalarial drug that also has no grapefruit interactions. The ABDA database currently contains grapefruit interactions with 55 drugs. So here is one of the list of grapefruit and medications that increase the effect:
Drug and trade name
- Amiodaron Cordarex®
- Bexaroten Targretin®
- Budesonid Entocort®
- Buspirone Bespar®
- Carbamazepin Tegretal®
- Cisapride not commercially available
- Colchicine Colchysate®
- Darifenacin Emselex®
- They dropped Multaq®
- Fentanyl Durogesic®
- Fesoterodin Toviaz®
- Ivabradin Procoralan®
- Ivacaftor Kalydeco®
- Midazolam Dormicum®
- Pimozide Orap®
- Praziquantel Cesol®
- Quetiapin Seroquel®
- Ranolazine Ranexa®
- Rupatadin Rupafin®
- Terfenadin Al®
- Tolvaptan Samsca®
- Triazolam Halcion®
- Zolpidem Stilnox®
Calcium antagonists:
- Nifedipine Adalat®
- Felodipin Modip®
- Lacidipin Motens®
- Nisoldipin Baymycard®
- Nitrendin Biotensin®
- Nimodipin Nimotop®
- Amlodipine Norvasc®
- Isradipin Vascal®
- Nilvadipin Nivadil®
- Lercanidipin Carmen®
- Manidipin Manyper®
- Gallopamil Procorum®
- Verapamil Isoptin®
Statins:
- Atorvastatin Lot®
- Lovastatin Mevinacor®
- Simvastatin Zocor®
Immunosuppressants:
- Ciclosporin Sandimmun®
- Everolimus Certican®
- Sirolimus Rapamune®
- Tacrolimus Prograf®
Phosphodiesterase-5 Inhibitor:
- Sildenafil Viagra®
- Tadalafil Cialis®
- Vardenafil Levitra®
Protein kinase inhibitors:
- Axitinib Inlyta®
- Crizotinib Halkori®
- Lapatinib Tyverb®
- Nilotinib Tasigna®
- Pazopanib Votrient®
- Sunitinib Sutent®
In addition, there are some medicines whose effects are impaired by grapefruit:
- Aliskiren Rasilez®
- Bilastin Bitosen®
- Nitrogen mustard derivatives:
- Cyclophosphamid Endoxan®
- Ifosfamid Holoxan®
Other fruits that interact with medicines
Types of fruit juice other than grapefruit juice can rarely interfere with medications. Most of these allow you to consume orange juice, apple juice or grape juice instead of grapefruit juice. However, orange or apple juice may cause an interaction with fexofenadine (Allegra) and aliskerin (Tekturna). You should be careful when eating anything made from bitter oranges (often used in jams), grapefruit (a citrus fruit with a similar taste to grapefruit but less tart), and limes. These fruits also contain furanocoumarins and can cause the same interactions as grapefruit. However, studies have not been conducted as frequently, which means the risk is not fully known.
Pomegranate, for example, is also a delicious fruit that is full of antioxidants and vitamin C. However, this superfood interacts with the breast cancer drug called Ribociclib. The manufacturer recommends that patients avoid pomegranate or grapefruit and medications of this type. These juices can increase the levels of ribociclib in the blood. This then leads to increased side effects such as infections, changes in blood cell counts, decreased appetite, nausea and vomiting, diarrhea, hair loss (alopecia) and fatigue.
Further medical information
It is increasingly being shown that more medications interact with other juices. Aliskiren is a renin inhibitor used to treat high blood pressure. Research has shown that drinking orange, apple, or grapefruit juice regularly or briefly before or after a dose of aliskiren may interfere with the absorption of the medication. Blood levels of the drug may fall and its antihypertensive effect may be impaired. So you should avoid drinking orange, apple or grapefruit juice during treatment with aliskiren unless your doctor recommends otherwise. Atenolol, a beta-blocker also used to treat high blood pressure and chest pain, may interact with orange juice. However, the health effects are not really known. Orange juice may block absorption and lead to lower levels of atenolol in the blood. Patients should also avoid consuming large amounts of orange juice to avoid fluctuations in atenolol blood levels.
Fexofenadine is a non-drowsy antihistamine that is available over the counter. However, this can interact not only with grapefruit juice, but also with apple and orange juice. In the case of fexofenadine, this causes blood levels of the drug to fall and the effectiveness of the antihistamine may be reduced. This interaction occurs through a different mechanism than CYP450 3A4. For this reason, it is recommended to take fexofenadine with water and not with fruit juice. Healthcare providers should be informed about what medications patients are taking, including prescription and over-the-counter medications, herbal supplements, and vitamins. Tell your pharmacist every time you start or even stop taking any medication. It is important to check for possible drug interactions. Warning labels on prescription bottles should be followed. If an interaction is identified, an alternative medication may be able to be prescribed and the interaction avoided.
Other possible interactions
There are numerous other grapefruit and medication interactions. So these are not exhaustive lists. Other juices such as apple and orange also interact with some medications. So how should you go about it? First of all, you should ask the pharmacy or doctor about additional interactions. You can also check other juices. Your pharmacist may place a label on the pack warning you of an interaction. Always consult your doctor or pharmacist to understand the importance of drug interactions. Follow prescription recommendations to avoid toxic drug levels and unpleasant side effects.
In summary, grapefruit disrupts proteins in the small intestine and liver that normally break down many medications. Eating grapefruit or drinking grapefruit juice while taking these medications may cause higher blood levels. With some medications, even small amounts of grapefruit can cause serious side effects. Therefore, you should avoid such a combination. Your pharmacy may label these medications with a warning about such interactions. Above all, make sure your doctor and pharmacist know whether you regularly consume grapefruit. They can help you decide whether it is safe to consume the citrus fruit while taking certain medications.
