Grapefruit and its juice can concentrate, or dilute, a number of common drugs including anti-cancer drugs and lipophilic statins, and it can also cause aromatisation (more oestradiol production) so you would be wise to find out if you can consume grapefruit juice or even large Seville Oranges when on drugs.
Compounds in grapefruit can concentrate drug effects, or dilute them!
This article has been updated twice since first published in 2012 by Chris Woollams, ex-Oxford University Biochemist.
A patient rang me back in 2011 about her terrible side-effects with her cancer drug, Taxol. Puzzled, because they were so severe (loss of hair, eyebrows, nails), we asked her some basic questions. When we asked about her diet, it turned out she ate a daily grapefruit for breakfast. She loved it.
We had already looked up the drug Taxol/Paclitaxel on the manufacturer’s website. ‘Do not consume grapefruit’, was written clearly on the home page. The oncologist had mentioned nothing about diet, but he had told her to stop taking all her dodgy vitamins and supplements!
Eating the fruit or drinking the juice actually had a far more dangerous effect than the combined effect of all her supplements!
The chemicals involved in grapefruit juice, Seville oranges and pomelos are called furanocoumarins. These are metabolized by CYP3A4 to compounds that bind to and block the active site of the enzyme, causing irreversible inactivation. CYP3A4 activity in the small intestine is thus impaired until you make more of it in its active form.
Grapefruit juice and sudden death?
Similar concerns have been expressed for the drugs Tamoxifen and Herceptin. But this is nothing new; there was a study on grapefruit Juice with cardiovascular drugs in 2004 (1). Unfortunately, certain new anti-cancer drug groups - CD4/6 drugs (e.g.Ibrance), PARP inhibitors (e,g, Olaparib), Tyrosine Kinase inhibitors (Tecentriq) and some PD-L1 immunotherapy drugs like Ipilimumab - all report conflict with Grapefruit juice.
In fact, the Lawson Health Research Institute in London, Canada, has studied the effects of mixing grapefruit juice with prescription drugs for almost two decades. When last we looked, they had 44 where grapefruit juice interferes. Of the 27 drugs added to the list since 2008, 13 of them can potentially cause sudden death if grapefruit juice is consumed with them! By 2013, the researchers were recording 83 drugs where grapefruit juice could cause issues (2).
Experts explain that certain medications react adversely to grapefruit juice by processing at a faster rate in your body, especially in the liver. This may create a significant increase in the drug’s potency, even to double dose levels! Interestingly the phenomenon can depend on the particular patient. The effects of the juice on particular drugs vary in severity from patient to patient. And while some drugs increased in potency, other drugs were actually weakened.
Have you been told that your statin and grapefruit juice may not mix?
For example, the FDA draws attention (3) to the fact that statins and grapefruit juice don't mix. The statins can concentrate, and stay in the body longer, causing both liver and muscle problems. In particular, the FDA name Atorvastatin (Lipitor) and Simvastatin. Did you doctor warn you of this?
The full spectrum of drugs in question can include cancer drugs, some statins, some anti-anxiety drugs, some high blood pressure drugs and some corticosteroids. And, as we said above, consuming grapefruit juice can also cause more aromatisation - the production of oestradiol in your fat stores by aromatase enzymes. Large Seville oranges can cause this too.
Many drugs are broken down or metabolized with the help of a vital enzyme, CYP3A4, in the small intestine. Grapefruit juice can block the action of CYP3A4, so instead of being metabolized, more of the drug enters the blood and stays in the body longer. The result: can be too much drug in your body. But the amount of the CYP3A4 enzyme in the intestine varies from person to person. So, grapefruit juice may affect people differently even when they take the same drug.
A few of the drugs that don't mix with grapefruit juice
Of course, new drugs are being launched all the time, so it is hard to give you the absolutely definitive list. All we can say is that the list of drugs includes:
Palbociclib (Ibrance), ribociclib, abemaciclib, ipilimumab, atezolizumab (tecentriq), ibrutinib, olaparib, niraparib, rucaparib, talazoparib, crizotinib, cyclophosphamide, viagra, dasatinib, erlotinib, imatinib, lapatinib, nilotinib, pazopanib, sorafenib, sunitinib, vandetanib, venurafenib, repaglinide, saxagliptin, albendazole, artemether, erythromycin, etravirine, halofantrine, maraviroc, praziquantel, primaquine, quinine, rilpivirine, saquinivir, budesonide-oral, colchicine, methylprednisolone-oral, atorvastatin, lovastatin, simvastatin, amiodarone, amlodipine, apixaban, cilostazol, clopidogrel, dronedarone, elerenone, ergotamine, felodipine, losartan, manidipine, nicardipine, nifedipine, nimodipine, nisoldipine, nitrendipine, propafenone, quinidine, rivaroxaban, sibutramine, sildenafil, tadalafil, ticagrelor, vardenafil, aprepitant, alfentanil-oral, buspirone, carbamazepine, dextromethorphan, diazepam, fentanyl-oral, fluvoxamine, ketamine-oral, lurasidone, methadone, midazolam, oxycodone, pimozide, quazepam, quetiapine, sertraline, triazolam, ziprasidone, estradiol, ethinylestradiol, cisapride, domperidone, cyclosporine, paclitaxel, tamoxifen, herceptin, perjeta, everolimus, sirolimus, tacrolimus, darifenacin, festerodine, solifenacin, silodosin, tamsulosin.
We suggest you raise the issue with your doctor, oncologist or pharmacist BEFORE taking any drug.
But there are other foods that don't mix with other drugs - like fermented foods, cheese, eggs and dried meats - have you been warned about which foods and which drugs?
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References:
- Interactions between grapefruit juice and cardiovascular drugs - Lawson Research Institute, 2004; David G Bailey, Gordon K. Dresser.
- Grapefruit–medication interactions: Forbidden fruit or avoidable consequences? David G. Bailey, George Dresser and J. Malcolm O. Arnold; CMAJ March 05, 2013 185 (4) 309-316;
- FDA - Grapefruit juice and some drugs don't mix - https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mix