Q. My son is on Tegretol to prevent seizures and one of the things he has to avoid is grapefruit. I have seen that grapefruit must be avoided by people taking other medicines. What could happen if he does eat some? The school system puts grapefruit in the school lunches.

A. Grapefruit increases blood levels of many medications, including Tegretol. That could lead to side effects such as dizziness, drowsiness, lack of coordination or nausea and vomiting.

Grapefruit can also boost the effects of some blood pressure medicines and cholesterol-lowering pills. One reader had this cautionary tale: “One of my healthy, hard-working professional friends took his Lipitor pill with grapefruit juice and had to be hospitalized. At the time, he had no idea that grapefruit juice enhances or multiplies the strength of this medication.”

We are sending you our Guide to Grapefruit Interactions for a more complete discussion and answers to frequently asked grapefruit questions.

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  1. Elise Villemaire

    I AM NOT RECOMMENDING THIS, but I have begun, with my doctor’s knowledge, to incorporate grapefruit juice as an element of my carbamazepine (Tegretol) treatment for seizures.
    After reading some studies on Pubmed (National Institutes for Health), it seemed clear that less drug could be taken (instead of mostly urinated unused into our public water systems) with a carefully taken grapefruit (pomegranate also works) juice supplement. I Take about 6 ounces of juice, then an hour or two later (after the juice’s effects on the liver are at their peak) I take a smaller (2/3rds for me) dose of carbamazepine. If I forget the juice I can just take my actual prescription. I’ve had no problems in the six months I have been self-supplementing and critically saving cash, since I am uninsured.
    I have no idea if there could be long term problems, but I am able because I can sense when my body is running low on the drug after 15 years of dependence. I am due for a blood test soon, but continuing to be seizure free is critical and only this lets me share my NON-RECOMMENDING story.

  2. Tami

    My son is also on Tegretol for seizures, along with a secondary medication, Keppra. We found out by accident about the grapefruit juice interaction, but you have to also be careful of drinks, especially sodas, containing grapefruit juice. He drank Squirt at a family party on a Sunday afternoon, and missed the next four days of school due to the intense side effects.
    Dizziness, nausea, eyes unable to track – he was miserable and couldn’t even walk to the bathroom without almost falling over! Make sure you make your son aware of the dangers of Squirt and Fresca, specifically – although there may be others. He is leaving for college in the fall, and I just pray he doesn’t have another week like that due to inadvertently ingesting a grapefruit product.

  3. A. Basilone

    I believe that drinking alcoholic beverages, mixed with grapefruit juice can boost the effect of the medicine so much, that even the utterly smoothest medicine taker would grow weary.
    AB 2009*

  4. WE

    Will eating or drinking citrus juices or “joint juice” affect my acid reflux?

  5. Heather

    It seems like if this effect could be applied consistently and predictably, that doctors could prescribe a smaller dose of an expensive medication along with a specified amount of grapefruit juice.

  6. S.H.

    If grapefruit boosts the effeccts of some prescription drugs (and some are pricy$$$) couldn’t doctors and patients take advantage of that fact and actually use and pay for less meds? LIKE if blood pressure meds are made more effective, the patient could cut the pill into smaller pieces, drink a little juice and save money?……I know the patient would have to be monitored more, but could it help and work for some folks? (I am not endorsing doing this, but could a smart doctor figure out a way to do it?)JUST WONDERING…..

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