Grapefruit juice seen as hindering some drugs
(April 8, 1999 12:18 a.m. EDT http://www.nandotimes.com) - Researchers have
found that drinking grapefruit juice before taking certain prescription
drugs may actually inhibit, rather than enhance, absorption into the body,
studies published this month indicate.
Although the studies did not involve tests on animals or humans, Drs.
Andrea Soldner and Leslie Benet at the University of California-San
Francisco found that grapefruit juice activates one of the body's naturally
produced mechanisms that keeps drugs from entering the bloodstream.
Their work is reported in the April issue of Pharmaceutical Research,
published by the American Association of Pharmaceutical Scientists. Benet,
a professor of biopharmaceutical sciences, is founder of the association.
Ordinarily, grapefruit juice is recommended to enhance the uptake of
several types of important medications, including calcium channel blockers
used to treat hypertension and protease inhibitors used to treat human
immunodeficiency virus.
The juice, usually used in concentrated form, works by decreasing levels of
an intestinal enzyme that would otherwise break down drug molecules before
they can move into the blood.
But Benet and Soldner found that this benefit disappears when the body
tries to absorb certain drugs. Instead, an unknown substance in grapefruit
juice interacts with another substance against other medications, including:
- Vinblastine (a cancer drug)
- Cyclosporine (an immunosuppressant used in organ transplant recipients)
- Losartin (a blood pressure control medication)
- Digoxin (used to treat congestive heart failure)
- Fexofenadine (used to treat allergy symptoms).
Benet said patients "already taking grapefruit juice with their medications
can continue to do so. However, for certain drugs we studied, such as
immunosuppressives and protease inhibitors, patients may get a further
increase in absorption by taking their drugs a couple of hours after a
glass of grapefruit juice."
On the other hand, Benet warned that "patients who have not previously
taken their drugs with grapefruit juice should be very cautious in doing
so, since we now recognize that depending on the drug, grapefruit juice may
either increase or decrease levels of drug in the blood."
Lee Bowman covers health and science for Scripps Howard News Service.
By LEE BOWMAN
Copyright 1999 Nando Media
Copyright 1999 Scripps Howard News Service
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