New Study Finds Grapefruit Juice Could Decrease the Absorption of Many Drugs
Alexandria, VA -- Drinking a glass of grapefruit juice with medications has long been known to help with the body's absorption of certain drugs. However, scientists at the University of California at San Francisco (UCSF) have now found that grapefruit juice may actually have a negative impact on the body's absorption of many widely-prescribed medications.
Grapefruit juice is known to improve the oral absorption of several important medications on the market by decreasing levels of an intestinal enzyme, known as CYP3A4, that would otherwise breakdown drug molecules before they reach the blood stream. These drugs include antihypertensive calcium channel blockers (i.e., felodipine, Plendil and HIV-protease inhibitors (i.e., saquinavir, Invirase).
In a study* published in the April 1999 issue of Pharmaceutical Research, an
American Association of Pharmaceutical Scientists (AAPS) publication, Dr. Andrea
Soldner and other scientists at UCSF demonstrate that grapefruit juice can
actually inhibit the body's absorption of certain drugs including:
Vinblastine (for combating cancer)
Cyclosporine (for supressing organ rejection following transplant)
Losartan (for controlling high blood pressure)
Digoxin (for treating congestive heart failure)
Fexofenadine (for alleviating allergy symptoms)
This inhibition occurs because an unknown substance in grapefruit juice activates one of the body's naturally-produced drug efflux mechanisms, known as P-glycoprotein, located in the intestinal tract. When grapefruit juice interacts with P-glycoprotein, the result is an increased likelihood that certain drugs will be stopped from entering the bloodstream.
These findings help to clarify some major discrepancies we've noticed in the
impact of grapefruit juice on various types of medications," said Dr. Leslie
Benet, founder of the American Association of Phar
Contact: Valerie Breslow
American Association of Pharmaceutical Scientists