Why you should never eat grapefruit before taking drugs

If you’re on medication, maybe think twice before tucking into your morning grapefruit. Taking drugs at the same time as eating grapefruit can exacerbate the effect of the drugs and cause serious side effects.

Grapefruit contains a chemical that affects your enzymes and makes the effect of many medicines much stronger than normal. The chemical furanocoumarins present in grapefruit, Seville oranges in limes inhibits enzyme cytochrome, the enzyme that inhibits drug-activation. The effect is present in half of all drugs.

Eating grapefruit before taking prescribed medication could have lethal consequences, according to the peer-reviewed Canadian Medical Association Journal. This is because grapefruit makes the effects of some drugs stronger as if the patient had taken a higher dosage.

Grapefruit and similar citrus fruits such as Seville oranges, limes and pomelos contain a chemical called furanocoumarins. This stops the enzymes in your stomach from breaking down drugs. The enzyme cytochrome P450 3A4 is found in your liver and intestines and it is responsible for breaking down many widely-used drugs. If the enzyme is deactivated then much more of the drug ends up in the bloodstream than was intended. This can lead to adverse side affects.

Drugs affected by grapefruit (according to NHS guidelines):

• Drugs used to treat cancer (crizotinib, dasatinib, erlotinib,everolimus, lapatinib, nilotinib, pazopanib, sunitinib, vandetanib, vemurafenib)
• Drugs used to treat or prevent infections (erythromycin, halofantrine, maraviroc, primaquine, quinine, rilpivirine)
• Drugs used to treat high cholesterol (atorvastatin, lovastatin, simvastatin)
• Drugs used to treat heart and blood vessel conditions (amiodarone, apixaban, clopidogrel, dronedarone, eplerenone, felodipine, nifedipine, quinidine, rivaroxaban, ticagrelor)
• Drugs affecting the central nervous system (oral alfentanil, buspirone, dextromethorphan, oral fentanyl, oral ketamine, lurasidone, oxycodone, pimozide, quetiapine, triazolam, ziprasidone)
• Drugs used to treat nausea (domperidone)
• Immunosuppressants (cyclosporine, everolimus, sirolimus, tacrolimus)
• Drugs used to treat urinary tract conditions (darifenacin, fesoterodine, solifenain, silodosin, tamsulosin)

Possible side effects of eating grapefruit whilst taking drugs:

Cases that have been reported include complete heart block, rapid heart beat, kidney damage, damage to bone marrow, bloodclot.

Sources:

https://www.nhs.uk/news/medication/prescription-drugs-and-grapefruit-a-deadly-mix/

Grapefruit–medication interactions: Forbidden fruit or avoidable consequences?
David G. Bailey, George Dresser and J. Malcolm O. Arnold

https://www.drugs.com/article/grapefruit-drug-interactions.html

See also:

Why you should never polish your shoes while drinking a beer