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NIGMS-funded Scientists Discover Chemicals in Grapefruit Juice that Cause Drug Reaction

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Brief Description:
Ever look at the warning label on some prescription medications, such as some high blood pressure meds, and wonder why you're being warned not to take that medication with grapefruit juice?

Transcript:
Schmalfeldt: Ever look at the warning label on some prescription medications, such as some high blood pressure meds, and wonder why you're being warned not to take that medication with grapefruit juice? It's because over 15 years ago researchers discovered a dangerous interaction between grapefruit juice and these medications. There are chemicals in grapefruit juice that interfere with the way your body absorbs the medication. Now, scientists funded by the National Institutes of Health know just which chemicals in grapefruit juice are responsible for this effect. A team of researchers at the University of North Carolina at Chapel School of Medicine have determined that chemicals known as furanocoumarins keep an enzyme in your digestive tract from metabolizing certain medications. Dr. Richard T. Okita is a program director in the Division of Pharmacology, Physiology and Biological Chemistry at the National Institute of General Medical Sciences. He explained how this works.

Okita: Essentially, it knocks out this protein in your GI tract. Normally this enzyme would metabolize the drugs and essentially prevent them from being absorbed or they would be absorbed in an inactive state. So by taking grapefruit juice with your drugs, what can happen is you'll have higher drug levels.

Schmalfeldt: So, basically, if you take these certain meds with grapefruit juice, your body gets a higher dose of the medication than that which was intended. As a result of this research, scientists have been able to develop methods that would permit the production of grapefruit juice that does not have the chemicals responsible for this effect. Will you be able to purchase this modified grapefruit juice at your grocery store any time soon? Dr. Okita said that's up to the manufacturers.

Okita: This is a complex process. So whether or not it will be commercially feasible in the short term, that would be up to the grapefruit producers.

Schmalfeldt: So, in the meantime, if your medication has a warning label referring to grapefruit juice, follow its advice and wash down those pills with water or some other kind of juice. But at least now you know why! The research was published in the May edition of the American Journal of Clinical Nutrition. From the National Institutes of Health, I'm Bill Schmalfeldt in Bethesda, Maryland.

This page was last reviewed on June 29, 2006 .

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