Rock doc: Grapefruit + medications = potential problem

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.

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.

If you are really dedicated to grapefruit consumption, your doctor may be able to substitute a new medication for one that’s 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 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.

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.