Return of the Killer Grapefruit ?

Red Grapefruit

Our mantra at Fooducate is to eat more fruits and vegetables. Grapefruit is a wonderful fruit from the citrus family, and once your palate adjusts to its tart surprise, it can be enjoyed as much as its sweeter cousin, the orange.

A single grapefruit is about 2 serving’s worth. Each serving is approximately 100 calories, has half your daily vitamin A requirements, over 100% of your daily vitamin C, 4 grams of fiber (15% of daily requirement), and despite the tartness – the equivalent of 4 teaspoons of sugar! Like all citrus fruit, it is packed with healthful antioxidants.

What’s not to love?

A lot, If you are taking certain types of medication.  The interaction can lead to an assorted range of maladies and even death. Over the last few decades, the number of relevant medications has risen to 85! This, according to a report recently published by Canadian researchers led by David Bailey, clinical pharmacologist, Lawson Health Research Institute. (See list at the bottom of this post).

It’s long been known that people on statins (cholesterol lowering medication) need to stay away from grapefruit, and grapefruit juice. But now, there are more drugs that could pose a danger.

What exactly is the interaction and why is it potentially lethal?

Grapefruit (but not oranges) contain chemical compounds called furanocoumarins that interact with certain orally administered drugs that are metabolized by an enzyme called cytochrome P450 3A4. The interaction can lead to an overdose of the drug. Overdosing can cause unwanted side effects.

How can you overdose if you take just one pill as prescribed?

Certain drugs are not absorbed very well by the body (their bioavailability is low) so a very large dosage is put in each pill. The required dosage may be only 5-10% of what’s actually in the pill. Most of the dose is flushed away with your bodily waste. What grapefruits can do is increase the bioavailability up to 100% and thus cause an overdose.

What to do if you are taking any drugs listed below and love grapefruit?

Speak with your doctor and pharmacist.

Here’s a list of the relevant drugs (source: CBC News)


  • Crizotinib.
  • Dasatinib.
  • Erlotinib.
  • Everolimus.
  • Lapatinib.
  • Nilotinib.
  • Pazopanib.
  • Sunitinib.
  • Vandetanib.
  • Venurafenib.


  • Erythromycin.
  • Halofantrine.
  • Maraviroc.
  • Primaquine.
  • Quinine.
  • Rilpivirine.


  • Atorvastatin.
  • Lovastatin.
  • Simvastatin.


  • Amiodarone.
  • Apixaban.
  • Clopidogrel.
  • Dronedarone.
  • Eplerenone.
  • Felodipine.
  • Nifedipine.
  • Quinidine.
  • Rivaroxaban.
  • Ticagrelor.

Central nervous system

  • Alfentanil (oral).
  • Buspirone.
  • Dextromethorphan.
  • Fentanyl (oral).
  • Ketamine (oral).
  • Lurasidone.
  • Oxycodone.
  • Pimozide.
  • Quetiapine.
  • Triazolam.
  • Ziprasidone.


  • Domperidone.


  • Cyclosporine.
  • Everolimus.
  • Sirolimus.
  • Tacrolimus.

Urinary tract

  • Darifenacin.
  • Fesoterodine.
  • Solifenacin.
  • Silodosin.
  • Tamsulosin.
  • MrBillWest

    Is there any research being conducted on using furanocoumarins to increase drug absorption? Smaller pill size can be a benefit for some. It could also cut cost of production.

    • Fooducate

      Don’t know, it’s beyond the scope of this blog.
      Would be interesting to find out…

      • Meristemi

        Some studies have been made on this regard, but we’re still far from an amount of evidences adequate for human use. In few cases (e.g. morphine) some animal data is available.

  • curious

    I am on nifedipine and my pharamacist said that the research has not been extensive enough to show that it is really an issue. I was told I could eat a grapefruit here and there, just not every day….was that bad advice? I LOVE grapefruit…I want to be able to eat it!

  • caylalily

    Though a hybrid, grapefruit is a mighty fine example of why I object to GMO foods. Then again, a new hybrid grapefruit with lower furanocoumarins, may be available within 10 years.