December 27, 2012 | Vol. 116 -- No. 36

Grapefruit + Medications = Potential Problem

We Americans are often told to eat more fruits and vegetables. Particularly this time of year, when New Year’s resolutions are still in strong force, a lot of us are trying to do better about what we eat. A breakfast of half a grapefruit and some peanut butter on a piece of toast sounds like it would be good for you, doesn’t it?

For millions of Americans who take prescription drugs, the answer may be no – such a breakfast might even be quite problematic for your health.

The difficulty arises because of certain effects in the compounds found in grapefruit and some other citrus fruits. When you eat them, they deactivate another chemical in the liver and small intestine that works to break down medication. The more such deactivation there is, the greater the effective dose of the medicine in your body because you aren’t breaking it down as you normally would.

“Taking one tablet with a glass of grapefruit juice is like taking five tablets with water,” said pharmacologist David Bailey when he spoke about the matter to the program NPR Shots.

And it seems the problem extends to more than just grapefruit. Seville oranges – which I love to eat at breakfast in tangy marmalade – may also act like grapefruit with respect to medications. So even something in your diet that seems as innocuous as toast and jam could be problematic.

According to a recent report on National Public Radio, the problem is one that’s increasingly important. In 2008 the number of medications that mixed poorly with grapefruit juice was 17. Now it’s 43.

Maybe you think that if you drink your grapefruit juice at breakfast but take your meds at supper you’d be OK. But, alas, that isn’t true. The effects of the grapefruit will still be with you in the evening.

If you are really dedicated to grapefruit consumption, your doctor may be able to substitute a new medication for one that is problematic. But if you want to stay on your current meds, the wise decision may be to forego the grapefruit.

Lists on the web about what medications are problematic with grapefruit are evidently incomplete. You should therefore check with your doctor or pharmacist about your own medications. But here are just some of the most commonly prescribed drugs that raise concerns with respect to grapefruit and certain other citrus products.

According to WebMD the drugs that can become problematic with respect to consuming grapefruit include:

Statins: Lipitor, Zocor and Mevacor

Impotence Drugs: Viagra

Psychiatric Drugs: Buspar, Valium, Zoloft

Pain Drugs: Methadone

Antihistimines: Ebastine

Anti-HIV medications: Invirase

Anti-arrhythmics: Cordarone

According to a Mayo Clinic website other medications like this include:

Antihistamine: Allegra

Calcium channel blockers: Procardia, Nimotop and Sular

Anti-seizure medications: Tegretol

Immunosuppressants: Neoral, Sandimmune, Prograf and Rapamune

According to a recent NPR article other medications in this group include:

Cancer drugs: Tarceva

Antibiotic: Erythromycin

Blood thinner: Plavix, Brilinta

Anti-psychotic: Seroquel

But to repeat, it looks to me like all of the lists on the web are incomplete. You need to investigate your own medications with your doctor or pharmacist. While you’re at it, confess to the authorities if you take herbal supplements or other similar substances. You might as well get them all checked out, with respect to each other as well as with respect to grapefruit. Perhaps that should be a New Year’s resolution for all of us who take medication.

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.

Reader Comments

(0)