Rock Doc: Citrus fruits aren’t always the answer

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 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,” pharmacologist David Bailey told 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 forgo the grapefruit.

Lists on the Internet 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, according to WebMD.com:

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 National Public Radio story, other medications in this group include:

Cancer drugs: Tarceva

Antibiotic: Erythromycin

Blood thinners: 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.

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.

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