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A is a food or part of a food that allegedly provides
medicinal or health benefits, including the prevention and treatment of
disease. Grapefruit juice has been touted as containing many compounds that can
reduce hardening of the arteries (atherosclerosis) and even the risk of cancer.
Grapefruit juice can, therefore, be justifiably referred to as a classic
nutraceutical. However, for many persons taking certain medications, grapefruit
juice might actually better be termed a “nutrapollutical!”
It turns out that grapefruit juice can directly or indirectly interact in
important ways with a number of medications. This is especially important since
grapefruit juice is consumed by approximately one fifth of Americans for
breakfast - a time of the day when medications also are commonly taken.
Grapefruit juice blocks special enzymes in the wall of the small intestine
that actually destroys many medications and prevents their absorption into the
body. Thus, smaller amounts of the drugs get into the body than are ingested.
When the action of this enzyme is blocked, more of the drugs get into the body
and the blood levels of these medications increase. This can lead to toxic side
effects from the medications.
Amazingly, this remarkable food-drug interaction was discovered completely
by accident over a decade ago! Researchers were whether alcohol
could interact with felodipine (Plendil) and used a solution of alcohol with
grapefruit juice to mask the taste of alcohol for the study. Researchers
discovered that blood levels of felodipine were increased several fold more
than in previous studies. This increased blood level caused an increase in the
effect and side effects of felodipine. Further research revealed that the
grapefruit juice itself was actually increasing the amount of the study drug in
the body.
Research about the interaction of grapefruit juice with drugs suggests that
compounds in grapefruit juice, called furanocoumarins (e.g. bergamottin), may
be responsible for the effects of grapefruit juice. Researchers believe that
furanocoumarins block the enzymes in the intestines that normally break down
many drugs. One glass of grapefruit juice could elicit the maximum blocking
effect, and the effect may persist for longer than 24 hours. Since the effects
can last for such a prolonged period of time, grapefruit juice does not have to
be taken at the same time as the medication in order for the interaction to
occur. Therefore, unlike similar interactions, where the interaction can be
avoided by separating the administration of the two interacting agents by a
couple of hours, administration of grapefruit juice with susceptible drugs
should be separated by 24 or more hours to avoid the interaction. Since this is
not practical for individuals who are taking a medication daily, they should
not consume grapefruit juice when taking medications that are affected by
grapefruit juice.
The grapefruit juice-drug interaction can lead to and
hazardous levels of certain important drugs.
These are medications with which grapefruit juice should NOT be consumed
unless advised by a doctor:
- Statins (Cholesterol Drugs): lovastatin (Mevacor), Lipitor,
Simvastatin Zocor, simvastatin/ezetimibe Vytorin
- Antihistamines: Ebastine, Seldane (terfenadine, taken off the U.S.
market)
- Calcium Channel Blockers (Blood Pressure Drugs): nimodipine (Nimotop),
Felodipine (Nitrendipine, Plendil), Pranidipine, nisoldipine (Sular),
nicardipine (Cardene), verapamil (Verelan)
- Psychiatric Medications: buspirone (Buspar), triazolam (Halcion),
carbamazepine (Tegretol), diazepam (Valium), midazolam (Versed), sertraline
(Zoloft)
- Intestinal Medications: cisapride, taken off the U.S. market
(Propulsid)
- Immune Suppressants: cyclosporine (Neoral), (tacrolimus) Prograf
- Pain Medications: Methadone
- Impotence Drug (erectile dysfunction): sildenafil (Viagra)
- Ant-HIV medication : saquinavir (Invirase)
- Antiarrhythmics: amiodarone (Cordarone)
Toxic blood levels of these medications can occur when patients taking them
consume grapefruit juice. The high blood levels of the medications can cause
damage to organs or impair the organs normal function, which can be dangerous.
If you or a family member are taking any of these medications, beware of the
“nutrapollutical” grapefruit juice.
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