Dear Alice,

I heard somewhere that drinking grapefruit juice with vitamins and/or prescription medicine is harmful. Is this true?

Dear Reader,

It’s hard to believe that a healthy drink like grapefruit juice would be a potential problem, right? Unfortunately, grapefruit and grapefruit juice does interact adversely with certain medications. In fact, there are over 80 medications that this citrus can interact negatively with and the number of interactions increases each year. So, if fresh grapefruit or grapefruit juice is a regular staple in your diet, talking to your health care provider or pharmacist before starting any new medications is a good idea.

Now, you may be wondering why this interaction happens. The potential interactions are two-fold: chemical compounds found in grapefruit interfere with processes in the body which can result in either an increase or decrease in the potency of certain medications. More specifically, the combination of grapefruit with some drugs results in more of the drug entering the bloodstream, which may lead to dangerous levels (higher than prescribed) of the drug in the body. This increases the potential for harmful and even life-threatening side effects. Conversely, grapefruit may also interact with the body in a way that reduces the absorption of some other medications, making them less effective.

Adverse interactions with grapefruit are indicated for medications that are used and prescribed for a variety of health issues, including:

  • Cardiovascular medications
  • Psychoactive drugs
  • Organ transplant rejection drugs
  • Immunosuppressants
  • Antibiotics
  • HIV medications
  • Cancer medication
  • Anti-anxiety
  • Anti-arrhythmia
  • Antihistamines
  • Urinary tract medications

Though this list is broad, not every medication used to treats the above conditions will interact negatively with grapefruit. In general, your health care provider and/or pharmacist can give you more information about any prescription and over-the-counter (OTC) medications, or herbal supplements and their possible side effects and contraindications — including whether or not grapefruit is safe to consume when using these drugs. Also, the information provided on the packaging or additional handouts that come with prescription and OTC medications will likely indicate whether avoiding grapefruit is advised. It’s also good to note that other citrus fruits such as Seville oranges, limes, pomelos, and tangelos have been identified as having the same chemical compound culprit as grapefruit, so if grapefruit is indicated, you may need to avoid these fruits as well. Lastly, if you’ve got to get your grapefruit fix, you may need to discuss your history of consuming this specific citrus with your health care provider and to see if the type or dosage of your medicine(s) can be adjusted accordingly. S/he may also be able to advise you on any non-interacting drugs that are available as an alternative.

Thanks for the juicy question!


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