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Grapefruit and Medicines: Interactions with Antibiotics and Pills

Although citrus fruits are reliable sources of food, many patients worry about the potential for drug-drug interactions. You may be given a prescription medicine with a warning label attached that recommends avoiding grapefruit or grapefruit juice while taking the drug. Antihypertensive drugs and grapefruit, for example, can cause side effects, but how and why do they occur in the first place? In this post we try to answer this question and provide you with a list of drugs that are not compatible with grapefruit.

Effect of pomelo grapefruit and medication

drug interaction grapefruit drug and juice consumption side effects antibiotics

Medicines 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 medication, as well as drug interaction with some of its close relatives such as Seville oranges, grapefruits, and minneola, contain a class of chemicals called furanocoumarins. These ingredients disrupt the normal function of the cytochromes. In fact, studies show that they increase the levels in the blood of over 85 drugs. This means that the grapefruit can increase the side effects of these drugs. It happens because this citrus fruit slows down the process that normally breaks down drugs in the intestines and liver.

cytochrome P450 after ingestion of grapefruit juice influences the metabolism of toxins

Interactions with grapefruit can therefore occur with common and important drugs. This happens, for example, with drugs that lower cholesterol, treat high blood pressure, or even cancer drugs. The juice affects how drugs are altered (metabolized) in the body for eventual elimination. This can change the amount of medication in the blood and lead to increased side effects or less effectiveness of the medication. New drugs are approved frequently, so it is wise to study your interactions with grapefruit juice. Contact your pharmacist or doctor to find out about possible interactions. Examples of common drugs that interact with grapefruit juice are cholesterol drugs like atorvastatin, lovastatin, simvastatin, felodipine, and other calcium channel blockers, clarithromycin (Biaxin), and loratadine (Claritin). Doctors report that some immunosuppressants cause kidney damage. Certain pain relievers can make breathing difficult when taken with grapefruit juice.

Grapefruit drug interaction

bitter orange with vitamin c interaction medicaments in the form of lozenges

Medicines or toxins are usually broken down in such a way that the body can eliminate them. Grapefruit or grapefruit juice can change enzymes in the body and affect how medicines interact with the body before it is eliminated. Grapefruit juice decreases the activity of the 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 that block the CYP3A4 enzymes. When grapefruit juice is consumed, the enzyme’s ability to break down the drug for elimination is reduced. This also increases the blood level of the drug, which creates a risk of new or worsened side effects. A whole fruit or 200 milliliters of grapefruit juice can block the CYP3A4 enzymes and cause toxic blood levels of the drug. Grapefruit interaction is not common with all drugs. Your doctor may choose an alternative medication.

antihypertensive drugs and grapefruit drug interaction check interaction

Side effects may vary depending on the interacting drug and possible side effects. These can range from abnormal heart rhythms to stomach bleeding and muscle pain to muscle breakdown, kidney damage, low blood pressure, difficulty breathing and dizziness. Other reactions can also occur. However, this will depend on the medicine and the levels of the drug in the blood. So, if you know about any potential interaction with grapefruit, you should ask your doctor to describe the possible side effects so they can learn how to spot them. Taking medication at any time other than while consuming grapefruit juice will not prevent the interaction. The effects of grapefruit juice on certain drugs can last for over 24 hours. Even if you are taking a medicine that is only given once a day, you should avoid the combination of grapefruit and medication for the entire duration of treatment. Therefore, follow the instructions on the package insert for each individual medication or ask your doctor.

Grapefruit and anti-infection medication or antibiotics

grapefruit and medication can affect the body

These anti-infection drugs, known as antimicrobial agents, differ greatly in how they work and how they break down in the body. Although antimicrobials are one of the most diverse categories of drugs, there are few known to have 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 different types of bacterial infections. A study comparing grapefruit juice with water in patients taking erythromycin showed that the juice increased blood levels of the drug by 84%. Excessive amounts of this drug can disturb the rhythm of the heart.

Female patient at the doctor's examination of the oral cavity

In addition to anti-malarial drugs, grapefruit also increases levels of the HIV drugs rilpivirine and maraviroc. This can affect the rhythm or function of the heart. Since 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 does not interact with grapefruit. The ABDA database currently contains grapefruit interactions for 55 medicinal substances. So here is one of the lists of grapefruit and medications that will increase the effects:

Drug and trade name

statins cholesterol lowering simvastatin 40 mg tablets interaction grapefruit patient in hospital

  • Amiodarone Cordarex®
  • Bexarotene Targretin®
  • Budesonide Entocort®
  • Buspirone Bespar®
  • Carbamazepine Tegretal®
  • Cisapride not available in stores
  • Colchicine Colchysate®
  • Darifenacin Emselex®
  • Dronedaron Multaq®
  • Fentanyl Durogesic®
  • Fesoterodine Toviaz®
  • Ivabradine Procoralan®
  • Ivacaftor Kalydeco®
  • Midazolam Dormicum®
  • Pimozid Orap®
  • Praziquantel Cesol®
  • Quetiapine Seroquel®
  • Ranolazine Ranexa®
  • Rupatadin Rupafin®
  • Terfenadine Al®
  • Tolvaptan Samsca®
  • Triazolam Halcion®
  • Zolpidem Stilnox®

Calcium antagonists:

  • Nifedipine Adalat®
  • Felodipine Modip®
  • Lacidipine Motens®
  • Nisoldipine Baymycard®
  • Nitrendipine Bayotensin®
  • Nimodipine Nimotop®
  • Amlodipine Norvasc®
  • Isradipine Vascal®
  • Nilvadipin Nivadil®
  • Lercanidipine Carmen®
  • Manidipin Manyper®
  • Gallopamil Procorum®
  • Verapamil Isoptin®


  • Atorvastatin Sortis®
  • Lovastatin Mevinacor®
  • Simvastatin Zocor®


  • Ciclosporin Sandimmun®
  • Everolimus Certican®
  • Sirolimus Rapamune®
  • Tacrolimus Prograf®

Phosphodiesterase 5 inhibitors:

  • Sildenafil Viagra®
  • Tadalafil Cialis®
  • Vardenafil Levitra®

Protein kinase inhibitors:

  • Axitinib Inlyta®
  • Crizotinib Xalkori®
  • Lapatinib Tyverb®
  • Nilotinib Tasigna®
  • Pazopanib Votrient®
  • Sunitinib Sutent®

Pieces of grapefruit and essential oil in bottles combined with herbs

In addition, there are some medicines whose effects are affected by grapefruit:

  • Aliskiren Rasilez®
  • Bilastine Bitosen®
  • Nitrogen mustard derivatives:
  • Cyclophosphamide Endoxan®
  • Ifosfamide Holoxan®

Other types of fruit that interact with medicinal products

Elderly patient with grapefruit interactions pill and glass with juice

Types of fruit juices other than grapefruit juice can rarely interfere with medication. For most of these, you can consume orange juice, apple juice, or grape juice instead of grapefruit juice. However, orange or apple juice can interact with fexofenadine (Allegra) and aliskerin (Tekturna). You should be careful when eating something 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 often, which does not fully disclose the risk.

nutritional supplements vitamins and minerals as grapefruit and medicines

For example, pomegranate is also a delicious fruit that is full of antioxidants and vitamin C. However, this superfood does interact with an anti-breast cancer drug called ribociclib. The manufacturer recommends that patients avoid pomegranate or grapefruit and drugs 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

doctor holds lemon with grapefruit and medication in both hands

So it is increasingly shown that more drugs interact with other juices. Aliskiren is a renin inhibitor used to treat high blood pressure. Research has shown that drinking orange, apple, or grapefruit juices regularly or briefly before or after a dose of aliskiren can interfere with the absorption of the drug. The blood level of the drug may decrease and its antihypertensive effect may be impaired. So you should avoid drinking orange, apple, or grapefruit juice while you are on 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 can 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.

old man in bathrobe holds grapefruit and medication in hand

Fexofenadine is a non-drowsy antihistamine that is available without a prescription. However, this can interact not only with grapefruit juice, but also with apple and orange juice. In the case of fexofenadine, this will lower the blood levels of the drug and the antihistamine may be less effective. This interaction occurs by a different mechanism than CYP450 3A4. For this reason, it is recommended that fexofenadine be taken with water and not with fruit juice. Healthcare providers should be informed about what medications patients are taking, including prescription and nonprescription drugs, herbal supplements, and vitamins. Let your pharmacist know every time you start or even stop taking any medication. It is important to look for possible drug interactions. Warning labels on prescription bottles should be followed. If an interaction is detected, an alternative drug may be prescribed and the interaction avoided.

Other possible interactions

grapefruit extract in a small bottle as an oil use as a natural remedy

There are numerous other interactions between grapefruit and medication. So these are not exhaustive lists. Other juices like apple and orange also interact with some drugs. So how should you go about doing this? In the first place you should inquire about the additional interactions in the pharmacy or the doctor. You can check out other juices too. Your pharmacist can put a label on the pack to warn you of any interaction. Always consult your doctor or pharmacist to understand the importance of drug interactions. Follow prescribing recommendations to avoid toxic drug levels and nasty side effects.

Citrus fruit cut in half with red pulp on a gray background

In summary, grapefruit disrupts proteins in the small intestine and liver, which many drugs normally break down. Eating grapefruit or drinking grapefruit juice while taking these medications can lead to higher blood levels. With some drugs, even small amounts of grapefruit can cause serious side effects. Therefore, you should avoid such a combination. Your pharmacy may mark these drugs with a warning about such interactions. Most importantly, make sure your doctor and pharmacist know if you consume grapefruit regularly. They can help you decide whether it is safe to consume the citrus fruit while taking certain medicines.