Grapefruit is very high in vitamin C and a great source of potassium. However it is also one of the most common culprits in food-drug interactions. Components in grapefruit called furanocoumarins block the action of an enzyme located in the small intestine called CYP3A4. This enzyme is also needed to help breakdown and metabolize certain medications. When this enzyme is blocked, it can result in too much of the medication in your system at one time which can lead to side effects (sometimes severe).
More recently, research has shown the opposite effect with some medications in regards to grapefruit consumption meaning you can get too little of the drug into your system. Some medications rely on transporters in the body to be absorbed. In this case the grapefruit juice blocks the transporter preventing the medication from getting absorbed into the body appropriately.
1Here is a list of common medications where grapefruit consumption must be avoided along with their common uses in treatment for various medical conditions:
- aliskiren (Tekturna) – blood pressure
- amiodarone (Cordarone) – heart arrhythmia
- astemizole (Hismanal) – allergies
- bedaquiline (Situro) – active Tuberculosis
- budesonide (Entocort) – Crohn’s, ulcerative colitis
- buspirone (Buspar) – anxiety
- ceritinib (Zykadia) – non-small cell lung cancer
- cerivastatin (Baycol) – cholesterol
- cilostazol (Pletal) – peripheral vascular disease
- cisapride (Propulsid, Prepulsid) – increase gastrointestinal motility
- clopidagrel (Plavix) – blood thinner
- colchicine – gout
- crizotinib (Xalkori) – cancer
- dasatinib (Sprycel) – leukemia
- dronedarone (Multaq) – heart arrhythmia
- eletriptan (Relpax) – migraines
- erlotinib (Tarceva) – pancreatic cancer
- etoposide (Vepesid) – cancer (chemotherapy)
- everolimus (Afinitor, Zortress) – cancer
- halofantrine (Halfan) – malaria
- ixabepilone (Ixempra) – breast cancer (chemotherapy)
- lapatinib (Tykerb) – breast cancer
- lovastatin (Mevacor) – cholesterol
- mifepristone (Mifeprex) – abortion pill
- nifedipine (Procardia) – blood pressure
- nilotnib (Tasigna) – leukemia
- pazopanib (Votrient) – kidney cancer
- pimozide (Orap) – Tourette syndrome
- primaquine – malaria, pneumonia
- quinidine (Quinaglute, Quinidex) – heart arrhythmia
- ranolazine (Ranexa) – chronic chest pain
- simvastatin (Zocor) – cholesterol
- sirolimus (Rapamune) – organ transplant rejection prevention
- sunitinib (Sutent) – cancer (chemotherapy)
- temsirolimus (Torisel) – kidney cancer (chemotherapy)
- terfenadine (Seldane) – allergies
- tolvaptan (Samsca) – congestive heart failure
- vandentanib (Caprelsa) – thyroid cancer (chemotherapy)
- vemurafenib (Zelboraf) – melanoma
- ziprasidone (Geodon) – schizophrenia, bipolar disorder
There are many other medications not listed above that may interact with grapefruit but to a lesser extent. If you are unsure whether or not you should consume grapefruit with your medication, ask your pharmacist and/or look on the bottle’s label for stated precautions.
Sources:
Grapefruit Juice and Some Drugs Don’t Mix. https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm292276.htm
1 Food Medication Interactions: The Foremost Drug – Nutrient Interaction Resource. 18th edition. 2015. Zaneta M. Pronsky, MS, RD, LDN, FADA; Dean Elbe, BSC (Pharm), BCPP, Pharm D; Keith Ayoob ED D, RD, FADA.