Dr. Tim Says...

Grapefruit Interactions

September 15, 2008

I have written before about the interaction with certain medications and grapefruit. It wasn't until about 2 years ago that scientists identified the exact substance in grapefruit that causes the problem. We now know that furanocoumarins (naturally-occurring substances found in grapefruit's juice) are the culprit.

The issue is how those furanocoumarins interact with the CYP3A4 enzyme made in the liver. The problem arises because of the way this enzyme acts on certain medications. Drinking grapefruit juice affects this enzyme and interferes with how they are broken down. We don’t know exactly how long after eating grapefruit or drinking the juice the effect wears off, however. Consequently the ongoing presence of the grapefruit in the body continues to have an effect on the system.

Interestingly, there are also CYP3A4 enzyme produced in the intestine that can interfere with the availability of drugs being absorbed into the bloodstream. As a result you should be aware that there may not be a safe time to take some cations when eating grapefruit or drinking grapefruit juice.

One of the questions that I have received after writing on this topic is just which drugs can be a problem. Part of the confusion comes from the fact that some are well documented in good research and others are only suspected at this time because the CYP3A4 enzyme is used for processing the medication in our bodies.

Eat well, eat healthy, enjoy life!

Dr. Gourmet

Known or possible interactions with grapefruit juice:

Albendazole (Albenza)
Alfentanil (Alfenta)
Alfuzosin (Uroxatral)
Almotriptan (Axert)
Alprazolam (Xanax)
Amiodarone (Cordarone)
Amlodipine (Norvasc)
Aprepitant (Emend)
Aripiprazole (Abilify)
Artemether (Riamet, Co-Artem)
Atorvastatin (Lipitor)
Bupropion (Wellbutrin, Zyban)
Buspirone (BuSpar)
Carbamazepine (Tegretol)
Carvedilol (Coreg)
Cilostazol (Pletal)
Cinacalcet (Sensipar)
Clarithromycin (Biaxin)
Clomipramine (Anafranil)
Codeine
Colchicine 5
Cyclosporine (Neoral)
Dapsone
Darifenacin (Enablex)
Delavirdine (Rescriptor)
Dextromethorphan
Diazepam (Valium)
Diltiazem (Cardizem, Tiazac)
Dofetilide (Tikosyn)
Efavirenz (Sustiva)
Eletriptan (Relpax)
Erlotinib (Tarceva)
Erythromycin (Eryc, E-mycin, Erythromid, Erybid)
Estrogens
Eszopiclone (Lunesta)
Etoposide (Vepesid)
Felodipine (Plendil)
Fentanyl (Sublimaze)
Fexofenadine (Allegra)
Fexofenadine (Allegra)
Fuvoxamine (Luvox)
Finasteride (Propecia, Proscar)
Gefitinib (Iressa)
Halofantrine (Halfan)
Haloperidol (Haldol)
Imatinib mesylate (Gleevec/Glivec)
Indinavir (Crixivan)
Itraconazole (Sporanox)
Losartan (Cozaar)
Lovastatin (Mevacor)
Methadone (Dolophine)
Methylprednisolone (Medrol)
Midazolam (Versed)
Mifepristone (Mifeprex)
Montelukast (Singulair)
Nelfinavir (Viracept)
Nicardipine (Cardene)
Nifedipine (Procardia)
Nimodipine (Nimotop)
Nisoldipine (Sular)
Ondansetron (Zofran)
Oxybutynin (Ditropan)
Paclitaxel (Taxol)
Pimozide (Orap)
Progestins
Propafenone (Rythmol)
Quetiapine fumarate (Seroquel)
Quinidine (Quinaglute, quinine, Quinidex)
Ramelteon (Rozerem)
Ritonavir (Norvir)
Saquinavir (Invirase)
Sertraline (Zoloft)
Sildenafil (Viagra)
Simvastatin (Zocor)
Sirolimus (Rapamune)
Solifenacin (Vesicare)
Tacrolimus (Prograf)
Tamoxifen (Nolvadex)
Tamsulosin (Flomax)
Tolterodine (Detrol)
Trazodone (Desyrel)
Triazolam (Halcion)
Vincristine (Oncovin)
Warfarin (Coumadin)
Zaleplon (Zonata)
Ziprasidone (Geodon)
Zolpidem (Ambien)

Last updated: 09/15/08