Why Grapefruit Affects Your Medication

What’s the deal with grapefruit juice and certain medications?

Why Grapefruit Affects Your Medication

There’s a lot to about grapefruit juice. It’s a sweet, yet tangy, alternative to orange juice in the morning. It’s full of vitamins A and C. It’s low in calories and high in fiber and potassium.

The National Institutes of Health includes grapefruit juice in its DASH (Dietary Approaches to Stop Hypertension) Eating Plan, a diet recommended to help reduce blood pressure.

But there’s at least one downside: You can’t have grapefruit juice when taking some prescription medications.

Why? Grapefruit juice can prevent specific medications from working as designed and/or create serious side effects.

“Grapefruit juice can slow down the breakdown of some drugs so you can build up toxic levels,” says Anthony Perre, MD, Chief of the Division of Outpatient Medicine at Cancer Treatment Centers of America® (CTCA).

“For patients with cancer, there are some contraindications with chemotherapy drugs that you have to watch out for.”

How does grapefruit juice affect medication?

Drugs are broken down, or metabolized, in the body by a variety of enzymes, which are substances that help produce a biochemical reaction.

Grapefruit, a hybrid citrus fruit of the sweet orange and pomelo varieties, contains furanocoumarins, chemical compounds that can interfere with those enzymes.

Specifically, furanocoumarins may block an enzyme called cytochrome P450 3A4 (CYP3A4), a critical component that helps the body break down drugs.

If CYP3A4 is blocked, drugs that are not metabolized may not work as designed. Or they may stay in the bloodstream longer, build up in the blood and become toxic. “This can lead to a greater concentration of drugs in the body,” Dr. Perre says.

“Patients may be at risk for muscle damage, heart arrhythmia or other conditions.” How grapefruit juice and medications interact depends on a variety of factors, especially the amount of CYP3A4 in the body.

That’s why the impact and side effects of this interaction vary from patient to patient.

Canadian researchers have identified at least 85 drugs that may interact with grapefruit juice.

For patients with cancer, the juice is believed to block the metabolization of some chemotherapy drugs, such as vincristine, used to treat small cell lung cancer, head and neck cancers and breast cancer, and docetaxel, used to treat prostate and breast cancers. Grapefruit juice also should be avoided when taking:

  • Statins prescribed to lower cholesterol
  • Calcium channel blockers, drugs intended to treat high blood pressure
  • Some anti-anxiety drugs
  • Corticosteroids intended to treat ulcerative colitis or Chron’s disease
  • Some drugs that treat abnormal heart rhythms
  • Some antihistamines

“Grapefruit is the most well-known example of a food-drug interaction,” Dr. Perre says.

Some less popular citrus fruits, such as Sevillian orange, pomelo and star fruit, have similar properties to grapefruit and should be avoided, as well. Dr.

Perre suggests patients ask their doctors about potential side effects of their prescription drugs and how they may interact with certain foods or other drugs.

Learn more about dangerous drug interactions

Source: https://www.cancercenter.com/community/blog/2019/08/whats-the-deal-with-grapefruit-juice-and-certain-medications

Grapefruit juice and medication

Why Grapefruit Affects Your Medication

Grapefruit juice and fresh grapefruit can interfere with the action of some prescription drugs, as well as a few non-prescription drugs.   Grapefruit juice can also be part of a healthful diet.   It has vitamin C and potassium—substances your body needs to work properly.   But it isn’t good for you when it affects the way your medicines work.

This interaction can be dangerous, says Shiew Mei Huang, acting director of the Food and Drug Administration’s Office of Clinical Pharmacology. With most drugs that interact with grapefruit juice, “the juice increases the absorption of the drug into the bloodstream,” she says. “When there is a higher concentration of a drug, you tend to have more adverse events.”

For example, if you drink a lot of grapefruit juice while taking certain statin drugs to lower cholesterol, too much of the drug may stay in your body, increasing your risk for liver damage and muscle breakdown that can lead to kidney failure.

Drinking grapefruit juice several hours before or several hours after you take your medicine may still be dangerous, says Huang, so it’s best to avoid or limit consuming grapefruit juice or fresh grapefruit when taking certain drugs.   Examples of some types of drugs that grapefruit juice can interact with are:

  • some statin drugs to lower cholesterol, such as Zocor (simvastatin), Lipitor (atorvastatin) and Pravachol (pravastatin)
  • some blood pressure-lowering drugs, such as Nifediac and Afeditab (both nifedipine)
  • some organ transplant rejection drugs, such as Sandimmune and Neoral (both cyclosporine)
  • some anti-anxiety drugs, such as BuSpar (buspirone)
  • some anti-arrhythmia drugs, such as Cordarone and Nexterone (both amiodarone)
  • some antihistamines, such as Allegra (fexofenadine)

Grapefruit juice does not affect all the drugs in the categories above. Ask your pharmacist or other health care professional to find out if your specific drug is affected.

How it works
Many drugs are broken down (metabolized) with the help of a vital enzyme called CYP3A4 in the small intestine. Certain substances in grapefruit juice block the action of CYP3A4, so instead of being metabolized, more of the drug enters the bloodstream and stays in the body longer. The result: potentially dangerous levels of the drug in your body.

The amount of the CYP3A4 enzyme in the intestine varies from one person to another, says Huang. Some people have a lot, and others have just a little—so grapefruit juice may affect people differently when they take the same drug.

While scientists have known for several decades that grapefruit juice can cause a potentially toxic level of certain drugs in the body, Huang says more recent studies have found that the juice has the opposite effect on a few other drugs.

“Grapefruit juice reduces the absorption of fexofenadine,” says Huang, decreasing the effectiveness of the drug. Fexofenadine (brand name Allegra) is available in both prescription and non-prescription forms to relieve symptoms of seasonal allergies. Fexofenadine may also be less effective if taken with orange or apple juice, so the drug label states “do not take with fruit juices.”

Why this opposite effect?

It involves the transportation of drugs within the body rather than their metabolism, explains Huang. Proteins in the body known as drug transporters help move a drug into cells for absorption.Substances in grapefruit juice block the action of a specific group of transporters. As a result, less of the drug is absorbed and it may be ineffective, Huang says.

When a drug sponsor applies to FDA for approval of a drug, the sponsor submits data on how its drug is absorbed, metabolized and transported says Huang. “Then we can decide how to label the drug.

”    FDA has required some prescription drugs to carry labels that warn against consuming grapefruit juice or fresh grapefruit while using the drug and the agency’s current research into drug and grapefruit juice interaction may result in label changes for other drugs as well.

Tips for Consumers

  • Ask your pharmacist or other health care professional if you can have fresh grapefruit or grapefruit juice while using your medication. If you can’t, you may want to ask if you can have other juices with the medicine.
  • Read the Medication Guide or patient information sheet that comes with your prescription medicine to find out if it could interact with grapefruit juice. Some may advise not to take the drug with grapefruit juice. If it’s OK to have grapefruit juice, there will be no mention of it in the guide or information sheet.
  • 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 as well if your medicine interacts with grapefruit juice.

Source:   FDA

Source: http://www.womenshealth.northwestern.edu/blog/grapefruit-juice-and-medication

Common Grapefruit Juice Drug Interactions — Drugs.com

Why Grapefruit Affects Your Medication

Medically reviewed by L. Anderson, PharmD Last updated on Aug 30, 2019.

Which drugs interact? | Why does grapefruit juice interact with drugs? | Possible side effects | Timing | Which other juices interact? | Common drugs that interact with grapefruit juice | Other resources

Which drugs interact with grapefruit juice?

While grapefruit is a nutritious fruit, many patients are concerned about the potential for drug interactions with grapefruit juice.

Maybe you've receive a medication prescription container with an affixed warning label that recommends you avoid grapefruit or grapefruit juice while taking the medication.

Grapefruit juice interactions can even occur with over-the-counter (OTC) drugs. But why is this so important?

  • Interactions with grapefruit can occur with common and important medications — such as those that lower cholesterol, treat high blood pressure, or even those that fight cancer.
  • Grapefruit juice affects how drugs are changed (metabolized) in the body for eventual elimination and can alter the amount of drug in your blood. This can lead to enhanced side effects or lower drug effectiveness.
  • New drugs are approved frequently, so it is wise to research your drug interactions with grapefruit juice drug with the Drugs Interaction Checker. Check with your pharmacist or doctor to confirm any interactions you may find.

Examples of common medications that interact with grapefruit juice include certain statin cholesterol drugs such as atorvastatin (Lipitor), lovastatin, simvastatin (Zocor), felodipine (Plendil) and other calcium channel blockers, clarithromycin (Biaxin), and loratadine (Claritin). Some immunosuppressants have been reported to cause kidney damage, and certain pain medications when mixed with grapefruit juice may be linked with depressed breathing.

Why does grapefruit interact with drugs?

Drugs or toxins are usually broken down (metabolized) so that they can be eliminated from the body. Grapefruit or grapefruit juice can alter enzymes in the body and affect how drugs are changed in the body before they are eliminated.

  • Grapefruit juice decreases the activity of the cytochrome P450 3A4 (CYP3A4) enzymes that are responsible for breaking down many drugs and toxins.
  • Grapefruit 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 decreased.
  • Blood levels of the drug may rise, resulting in a risk for new or worsened side effects.
  • One whole fruit or 200 milliliters of grapefruit juice (a bit less than one cup) can block the CYP3A4 enzymes and lead to toxic blood levels of the drug.

Not all drugs in any one drug class usually have a grapefruit interaction, so usually your doctor can select an alternative medication.

If you drink grapefruit juice, always have your pharmacist run a drug interaction check with your medications to rule out an interaction before you combine them.

What side effects are possible?

Side effects can vary the interacting drug and possible side effects. 

Side effects can range from abnormal heart rhythms, stomach bleeding, muscle pain, muscle breakdown, kidney damage, low blood pressure, difficulty breathing, sedation, and dizziness.

Other reactions may occur — it depends on the drug and the levels of the drug in the blood.

If you have been warned about a possible drug interaction with grapefruit, ask your healthcare provider to describe the possible side effect and learn how to recognize it.

Can I take my medicine at a different time from grapefruit juice  to prevent the interaction?

Taking medications at a different time from when grapefruit juice is consumed will not prevent the interaction. The effects of grapefruit juice on certain medications can last for over 24 hours. So, even if you take a medicine that is given only once per day, grapefruit and grapefruit juice should still be avoided for the entire treatment period.

In some cases, you may be able to drink smaller quantities of grapefruit juice, so you should follow the directions on the patient information leaflet for each individual drug or ask your healthcare provider.

What other types of juice interact with drugs?

Other kinds of fruit juice besides grapefruit juice may rarely interfere with medications. For most medications, orange juice, apple juice, or grape juice can be consumed instead of grapefruit juice without any concern for an interaction. However, orange or apple juice can cause an interaction with fexofenadine (Allegra) and aliskerin (Tekturna).

You should use caution when eating anything made with the seville orange (often used in marmalades), the pomelo (a citrus fruit with a similar flavor to grapefruit but less tart), and limes. These fruits also contain furanocoumarins and may cause the same interactions as grapefruit. Studies with these fruits are not as frequent, so their risk level is not fully known.

Pomegranate juice (from a berry) is a delicious fruit that is full of antioxidants and vitamin C. However, this «superfood» has an interaction with the breast cancer treatment ribociclib (Kisqali), as noted in product labeling.

The manufacturer recommends that patients avoid pomegranate or grapefruit and their juices while taking Kisqali.

These juices can increase the blood levels of ribociclib, leading to enhanced side effects such as infections, changes in blood cell counts, reduced appetite, nausea and vomiting, diarrhea, hair loss (alopecia), and fatigue.

Increasingly, more drugs are being shown to interact with other juices. Aliskiren (brand name: Tekturna) is a renin inhibitor medication used to treat high blood pressure.

Research has shown that drinking orange, apple, or grapefruit juices regularly or within a short period before or after a dose of aliskiren can interfere with the absorption of the medication. Blood levels of the drug may decrease, and its blood-pressuring lowering effect may be compromised.

You should avoid drinking orange, apple, or grapefruit juice during treatment with aliskiren, unless your doctor advises otherwise. 

Atenolol, a beta blocker agent also used to treat high blood pressure and angina (chest pain) may have an interaction with orange juice, but the health implications are not really known. Orange juice may block the absorption and lead to lower levels of atenolol in the blood. Patients should avoid consuming large amounts of orange juice to prevent fluctuations in atenolol blood drug levels.

Does Allegra interact with orange juice?

This is one of the most well-known orange juice drug interactions and one of the first ones identified. But it's interaction is a bit different.

Fexofenadine (Allegra), a popular non-drowsy antihistamine available over-the-counter (OTC) can interact not only with grapefruit juice, but also with apple and orange juice. However, in the case of fexofenadine, blood levels of the drug go down and the effectiveness of the antihistamine may be reduced.

This interaction occurs by a different mechanism than CYP450 3A4, but nonetheless, it is recommended that fexofenadine be taken with water, and not fruit juice.

Talk to your healthcare provider

Health care providers should be informed of which medications patients are taking, including any prescription and OTC drugs, herbal supplements and vitamins. Update your pharmacist any time you start or even stop taking a medication. It is important to check for potential drug interactions

Warnings labels on prescription bottles should be followed. If an interaction is found to occur, it may be possible that an alternative medication can be prescribed and the interaction can be avoided.

Common drugs that interact with grapefruit

Examples of some of the most common grapefruit or grapefruit juice drug interactions that can occur include:

Other resources

There are numerous other drug interactions with grapefruit and grapefruit juice; this is not a complete list.  Other juices, apple and orange, are now also being found to interact with some medications. How should you proceed?

  • Additional grapefruit juice drug interactions, and interactions with other juices, can be researched in the Drug Interaction Checker. You can also check your Patient Medication Guide that accompanies your prescription, and your pharmacist may include a label on your bottle warning you of an interaction.
  • Always be sure to consult with your doctor or pharmacist to understand the significance of any drug interaction, and follow prescription recommendations to help avoid toxic drug levels and unpleasant side effects.
  • You might also consider joining the Drugs.com Grapefruit Support group. Here you can chat about this topic at more length, review the latest questions and keep up to date with recent news about grapefruit juice interactions.

Sources

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  2. Product Information. Ibrance (palbociclib). Pfizer U.S. Pharmaceuticals Group, New York, NY. Accessed October 6, 2019.
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    FDA Consumer Health Articles. Grapefruit Juice and Some Drugs Don't Mix. Accessed August 31, 2019 at https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mix

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  7. Mayo Clinic. Consumer Health. I to drink grapefruit juice but hear that it can interfere with some prescription medications. Is that true? Accessed March 30, 2019 at http://www.mayoclinic.org/healthy-lifestyle/consumer-health/expert-answers/food-and-nutrition/faq-20057918
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    Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? CMAJ. 2012. Accessed March 30, 2019.

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    Pharmacy Times. Accessed March 30, 2019 at http://www.direct-ms.org/wp-content/uploads/2018/01/Grapefruit-juice-drug-reactions.pdf

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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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Source: https://www.drugs.com/article/grapefruit-drug-interactions.html

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