New Reason Seniors May Need to Avoid Grapefruit,
Other Juices with Medications
Life-saving drugs may become ineffective, if patient
consumes grapefruit or even other common fruit juices, including orange
and apple
Consult
with your doctor or pharmacist before taking any medications
with grapefruit juice or other fruits and juices
Aug. 19, 2008 – Drugs often prescribed for senior
citizens fighting life threatening conditions, such as heart disease,
cancer, organ-transplant rejection and infection, may become ineffective
if the patient consumes grapefruit or even other common fruit juices,
including orange and apple.
Scientists and many consumers have known for years
that grapefruit juice can increase the absorption of certain drugs -
with the potential for turning normal doses into toxic overdoses.
Now, the researcher who first identified this
interaction is reporting the new evidence that common fruit juices can
do the opposite - substantially decrease the absorption of drugs,
potentially wiping out their beneficial effects.
The study provides a new reason to avoid drinking
grapefruit juice and these other juices when taking certain drugs, the
researcher says. These findings - representing the first controlled
human studies of this type of drug-lowering interaction - were described
today at the 236th National Meeting of the American Chemical Society.
"Recently, we discovered that grapefruit and these
other fruit juices substantially decrease the oral absorption of certain
drugs undergoing intestinal uptake transport," says study leader David
G. Bailey, Ph.D., a professor of clinical pharmacology with the
University of Western Ontario in London, Ontario. "The concern is loss
of benefit of medications essential for the treatment of serious medical
conditions."
Bailey and colleagues announced almost 20 years ago
the unexpected finding that grapefruit juice can dramatically boost the
body's levels of the high-blood-pressure drug felodipine, causing
potentially dangerous effects from excessive drug concentrations in the
blood.
Since then, other researchers have identified
nearly 50 medications that carry the risk of grapefruit-induced
drug-overdose interactions. As a result of the so-called "Grapefruit
Juice Effect," some prescription drugs now carry warning labels against
taking grapefruit juice or fresh grapefruit during drug consumption.
In the most recent research, Bailey's group had
healthy volunteers take fexofenadine, an antihistamine used to fight
allergies. The volunteers consumed the drug with either a single glass
of grapefruit juice, water containing only naringin (substance in
grapefruit juice that gives the juice its bitter taste), or water.
When fexofenadine was taken with grapefruit juice,
only half of the drug was absorbed compared to taking the drug with
water alone, Bailey says. Loosing half of the amount of drugs taken into
the body can be critical for the performance certain drugs, he points
out.
They also showed that the active ingredient of
grapefruit juice, naringin, appears to block a key drug uptake
transporter, called OATP1A2, involved in shuttling drugs from the small
intestine to the bloodstream. Blocking this transporter reduces drug
absorption and neutralizes their potential benefits, the researchers
say.
By contrast, drugs whose levels are boosted in the
presence of grapefruit juice appear to block an important drug
metabolizing enzyme, called CYP3A4, that normally breaks down drugs.
"This is just the tip of the iceberg," Bailey says.
"I'm sure we'll find more and more drugs that are affected this way."
To date, grapefruit, orange and apple juices have
been shown to lower the absorption of etoposide, an anticancer agent;
certain beta blockers (atenolol, celiprolol, talinolol) used to treat
high blood pressure and prevent heart attacks; cyclosporine, a drug
taken to prevent rejection of transplanted organs; and certain
antibiotics (ciprofloxacin, levofloxacin, itraconazole).
But additional drugs are likely to be added to the
list as physicians become more aware of this drug-lowering interaction,
Bailey says.
Orange and apple juices also appear to contain
naringin-like substances that inhibit OATP1A2, Bailey says. The chemical
in oranges appears to be hesperidin, but the chemical in apples has not
yet been identified, the researchers notes.
Bailey advises patients to consult with their
doctor or pharmacist before taking any medications with grapefruit juice
or other fruits and juices. Unless it is known to be a problem, he
recommends taking most medications only with water. This research was
funded by grants from the Canadian Institutes of Health Research and the
United States Public Health Service.
The American Chemical Society — the world's largest
scientific society — is a nonprofit organization chartered by the U.S.
Congress and a global leader in providing access to chemistry-related
research through its multiple databases, peer-reviewed journals and
scientific conferences. Its main offices are in Washington, D.C., and
Columbus, Ohio.
Keep up with the latest news for senior citizens, baby
boomers
Consult
with your doctor or pharmacist before taking any medications
with grapefruit juice or other fruits and juices