Grapefruit + prescription drug = overdose

There are 44 prescription drugs on the market today that should never be combined with grapefruit. That's because the sour fruit (and some other, closely related, kinds of citrus) contain chemical compounds called furanocoumarins that prevent your body from metabolizing certain prescription drugs. Essentially, the grapefruit creates an artificial overdose where one tablet packs the power (and side effects) of 20. The CBC has a full list of the drugs, which includes cancer drugs, cholesterol-lowering drugs, and drugs to treat problems of the urinary tract. Wikipedia has more about why this interaction happens.



  1. My doctor’s office has giant posters.


    translated into 15 languages.

  2. Thank you for posting this. I am on one of those drugs and drink grapefruit juice sometimes on the weekends – and had no idea.

  3. Its not all grapefruit equally though. Some cultivars were found to not have the bad compounds in them. Wish I had the link, my fruit nerd friends were deep into the research since they grew collectively 30+ types of grapefruit and wanted to know which were safe with their medications.

    1. Radio the other day mentioned that some university has been breeding grapefruits that are safe with statins and other drugs.

      Meanwhile, noticing quinine there – no grapefruit&tonic?

      1. Barely any quinine in tonic anymore, even the fanciest ones. Certainly not enough to be considered “medicinal.”

      This article has the link to the publication

  4. So some 44 prescription drugs could pull the same punch at 5 % of the dosage, and toxicity, if they were rolled into a pill with those furanocoumarins? Is there research into that?

    1. There actually is, but most of the cost of these drugs has little to do with the cost of the raw materials. Businesses don’t want to spend $100,000+ to get approval on a new drug formulation just to add grapefruit to it.

      1. Yeah, but that only applies to people living under regimes with these sorts of rules.  Charities that are trying to get medication in third-world countries that don’t have these problems and where the cost of drugs is a significant problem could probably use this technique.  As a bonus, they might be able to pay people to grow the grapefruits and others to refine them.

  5. Grapefruit also interferes with a lot of anti-seizure medications, but those aren’t covered in the article. Worth looking into if you’re taking one (or know someone who is).

    1.  Indeed.  It was one of the things I rather disliked about carbamazepine (a.k.a. Tegretol) when I was taking it.

      Although I’ll admit I was more bothered by fact that you’re not supposed to drink alcohol while taking it.

  6. Also take note that grapefruit is used as a flavoring in some foods, especially sodas. We had a patient on Lipitor showing signs of rhabdomyolysis. Turns out he was drinking several Frescas each day and didn’t see what that had to do with those grapefruit warning labels we put on every bottle.

  7. Back in August of 2008 there was also a story out about orange juice not mixing well with prescription drugs either. Is this because of mixing grapefruit with orange juice, or is it just a citrus thing?

    I haven’t seen the warnings- are they specifically pointing out grapefruit or other things too (like other citrus)?

  8. The Coles Notes version:  when your doctor prescribes a drug, the dosage is based on certain assumptions about your body.  Drugs can be broken down and changed into different compounds as they move through the body.  Enzymes can make the drug’s molecules inert or less effective, some of the drug will move through parts of the body where it has no effect, some of it gets filtered by the kidneys, etc.  The goal is to have enough of the drug, at the right place, for a long enough duration to be effective.  So to meet that goal, you have to know how the drug is broken down (the different enzymes, excretion, etc.), how fast it breaks down, what’s the minimum dose that is effective in the treatment population, etc. etc. etc.   Knowing all of that, and making the assumption that the patient’s body will have the same rates of metabolism, the doctor makes the prescription.

    It’s like trying to make enough cookies to fill a delivery truck, but there’s a wild pack of Cookie Monsters roaming the bakery and NOM NOM NOMing.  In order to fill the truck, you’ll have to make a full truckload PLUS enough cookies to keep the monsters busy.

    The grapefruit problem, as it shall be known ;), is about enzyme Cytochrome P450 3A4.  The enzyme is supposed to go NOM NOM NOM like a good Cookie Monster, but the chemical in the grapefruit stuffs a giant marshmallow in the monster’s mouth, so he can’t NOM.

    The result is that you make way too many cookies and you have to eat all the extras and you become a Hutt and the world explodes.  Or, uh, more of the drug acts on your system than was expected, and you become unwell, and the world explodes.

    That was supposed to be the quick version…

  9. Who eats grapefruit? Seriously, it has to be the worst of all fruits. I’m shocked they even sell it in the market. Some Israeli parents serve grapefruit for breakfast every morning because its bitter taste evokes the suffering of the Jews.

    The only time it I can stomach it is if you juice it, add a *ton* of sugar and some bubbles. But then I’m just drinking sugar water with a little grapefruit flavoring.

    1. First, quit sugar.  Grapefruits are naturally sweet, but if you’re a sugar junkie your sweet receptors will be deadened.   They’ll come back in a couple months.

      For a shortcut, drop a Miracle Fruit Tablet and then try eating it – it’s like a totally different fruit – I actually find them too sweet without the sour flavor masking it!

    2. Pah, I pity the unfortunate souls who have never developed an adult appreciation for bitter foods.

      And don’t tell me you’re a super-taster. I’ve done the tests and can taste all the bitter compounds, and still love grapefruit.

    3. I eat 1/2 graperfruit every morning.But I also like Sour Patch Kids, those sour cherry candies, Gr.Fruit juice, lemonade, limeade, etc.

  10. My mom takes transplant related drugs that can be negated by grapefruit, which is sad since she’s the only one in the family who ever really liked them.

    /edit: also grapefruit are call that because they grow in clusters on the tree so stop being a smart ass

  11. Knowing this would have been nice when I was on buspirone.  Not that I’m a big fan of grapefruit, but as toasterslie and Dlo Burns mentioned, some tasty items have it as flavoring. I don’t remember if I ever had any Fresca during that time, but I ended up okay.

  12. Can we all say “Grapefruit Prohibition”? After all, the alcohol prohibition was a deadly failure and the marijuana prohibition is a deadly failure, so let’s (for the sake of the children) have a grapefruit prohibition. All we have to do is demonize the plant, arrest hundreds of thousands of people every year for possessing it and create a massive black market for it – then we’ll have achieved the exact same results that the alcohol and marijuana prohibitions have. 

  13. Yep, familiar with this. I was told to stop eating grapefruit when my chemo began because it can reduce efficacy of drug. And now that I’m on hormone therapy for cancer, it’s newly verboten. Used to love it!

    1. Xeni, I would have posted this just as a random addition somewhere in the thread, but it might be important to you: don’t drink to much Earl Grey (and other stuff with Bergamott in it). The same mechanism as in Grapefruit. See Wikipedia, for a start.

      BTW, since maybe spring will start somewhere on the northern hemisphere: allergics are affected as well. Cetirizine and allied antihistaminics may be metabolized differently when you take these plant metabolites. Don’t go crazy about it, but be aware.

  14. It also increases the duration though not general potency of opiates, which can be useful when you’re trying to increase the efficacy of your prescription meds during a hard month. It’s definitely good to be aware of though. 

  15. Geez. My (elderly) Dad is on Lipitor, among other drugs – Lipitor’s definitely on the list, though – and eats at LEAST a grapefruit every day. He’s crazy about grapefruit.

    Going to ask him to talk to his doctor about this…

  16. Have 10 gallons of grapefruit wine fermenting away. I wonder if the fermentation process makes any difference?

  17. Guys. Ask your pharmacist. They spent their entire college education learning about just these issues and they will explain what the risks of grapefruit will be. If yours won’t make some general statements about “very dangerous” vs. “probably fine, just look out for symptom X”, then get a new pharmacist. 

  18. I am actually drinking Fresca right this very moment, which is odd because I don’t typically drink Fresca. While I enjoy the occasional Fresca, I’m quite surprised that any active components of natural grapefruit  can be found in this tasty stew of acids, Aspartame, “natural & artificial flavors,” vegetable gums, preservatives, and, believe it or not, “ester of rosin” and “acacia.” Fresca is made of trees!

  19. One of my medications has this interacting, good thing I’ve always despised grapefruit. I find it odd that so many people are unaware of this. When I get my medications filled, there are brightly colored stickers on the pill bottles with warnings.

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