Nurse's Notes
2005 May View
WHAT’S THE STORY ABOUT GRAPEFRUIT?
Here we live in the beautiful Coachella Valley, home to the growth of
some of the tastiest grapefruit in the United States, and we’re told
we can’t eat it because we are on a certain medicine? What’s that all
about?
Grapefruit, as opposed to other citrus fruits, has several enzymes
which interact with some drugs in the intestines, changing the way the
drugs are absorbed and/or excreted. Consequently, when eaten within
several hours of taking the drug, the drug may become stronger or
weaker in the body. Weaker means it won’t work as well—stronger means
the patient may have a reaction or side-effect which would not happen
with normal dosing.
Only certain classes of drugs are affected by grapefruit (and
grapefruit juice). These are benzodiazepines (tranquilizers, such as
Xanax or Halcion), calcium channel blockers (used for high blood
pressure, irregular heart beats or sometimes angina), statins, used to
lower cholesterol, especially lovastatin (Mevacor) and simvastatin (Zocor),
ergot drugs which are used for migraines, immune suppression drugs
taken by patients who have had transplants, and protease inhibitors
which are used by folks with HIV.
Grapefruit is not the only type of food that can cause problems with
some drugs. Drinks with caffeine (coffee, tea, colas) can increase
side effects with some asthma drugs. Caffeine also can be a stomach
irritant, so be careful with it if you are taking a lot of ibuprofen,
aspirin or naproxyn.
Milk, would you believe! Calcium prevents the absorption of some
antibiotics, so ask you doctor or pharmacist if you should be drinking
milk if you are taking an antibiotic.
Alcohol—probably not a good idea to take in much alcohol if you are
taking a lot of medicine. Alcohol is detoxified in the liver and of
course can cause liver damage over the long haul, especially when
taken in excess. Combine that with acetaminophen (Tylenol) and you
have a much higher risk of damage. Alcohol also diminishes the effects
of antidepressants and can worsen the side effects of other drugs.
Fiber drinks, like Metamucil. Fiber binds with many drugs and thus
decreases their effectiveness. Fiber drinks should not be used if you
are on constipating medicine, such as opiates for pain.
And finally, our old friend, cranberry juice—the favorite drink of
choice for bladder infections. There have been reports in the
literature of increased bleeding with the use of cranberry juice and
Coumadin or other blood-thinners.
Best advice! When you get a new drug, ask your doctor or pharmacist
about how to take the drug—with or without food—and what foods, if
any, to avoid.
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