Q & A
By C. CLAIBORNE RAY
Published: April 12, 2005
Grapefruit and Pills
Q. Why are patients taking several widely prescribed medicines warned against consuming grapefruit or grapefruit juice?
A. Grapefruit interacts with an enzyme, found mostly in the lining of the digestive tract, that breaks down both the fruit and many drugs.
As a result, less of the enzyme is available to work on the drugs, and higher-than-normal amounts go into the bloodstream rather than being broken down. For some drugs, the effective dose is so much higher that it can be dangerous or even fatal.
The enzyme is called P450 34A. In 1989, scientists discovered that grapefruit juice could interfere with the digestion of one of the blood pressure medications called calcium channel blockers. Since then, the list of drugs with grapefruit warnings has grown.
Some widely prescribed cholesterol-lowering drugs known as statins, including Lipitor, are of special concern; extra-high levels of the drug can cause damage to the muscles or kidneys. The list also includes some anti-anxiety drugs, antidepressants and sleeping pills; some AIDS drugs, heart drugs and blood thinners; some drugs to fight rejection of organ transplants; and some antibiotics, among many others.
The effect is long lasting, persisting 24 hours or more, so eating grapefruit in the morning and taking the drug at night won't help.
For a few drugs, grapefruit activates another digestive chemical, P-glycoprotein, and may prevent full amounts of the drugs from entering the bloodstream.
Carefully read the label and inserts when taking any new drug; ask your doctor about other possible food and drug interactions, too. C. CLAIBORNE RAY
Drawing (Drawing by Victoria Roberts)