A substance in grapefruit juice improves the absorption of sirolimus, an experimental cancer drug.

Many patients have been warned not to drink grapefruit juice when taking certain medications.  That’s because enzymes in grapefruit juice can cause too much of some drugs to be released into your body, leading to serious health problems, including the potential for overdose.

But researchers at the University of Chicago have turned that negative into a positive. They found that a substance in grapefruit juice called furanocoumarin improved absorption of an experimental drug in cancer patients, allowing for lower dosages and reduced side effects.

“It’s a very interesting way of using a known food-drug interaction as a means of getting better drug levels into cancer patients,”  said Dr. Jerry Avorn, chief of the Division of Pharmacoepidemiology and Pharmacoeconomics at Brigham and Women’s Hospital, in an interview with ABCNews.com.

Researchers were challenged to find a solution to the problem of poor absorption for a drug called sirolimus. Only small amounts of sirolimus are absorbed into the bloodstream, too low to have a medical benefit for cancer patients.  However, higher dosages can increase patient side effects, such as nausea and diarrhea.  Then, Dr. Ezra Cohen, who led the study’s research team, recalled that grapefruit juice can increase the blood levels of some drugs.

The Florida Department of Citrus supplied the research team with grapefruit juice rich in furanocoumarin. (Supermarket grapefruit juice did not contain enough of this substance to have an effect.)  This potent juice increased sirolimus levels by 350 percent, allowing dosages to be reduced from 90 milligrams to 25-35 milligrams per week.

Besides reducing the potential for side effects, the lower dosages may have another benefit:  reduced costs.

“The cost of cancer treatments is very problematic for a lot of patients,” said Dr. Avorn.  “If this were to pan out in subsequent studies, this could really be a boon in terms of affordability of these drugs.”

Though the sirolimus was not found to be effective in fighting cancer, the study results hold promise as a way to beneficially boost blood levels of other drugs. Despite the promising results, it’s important to emphasize that you should avoid mixing grapefruit juice and various medications on your own.

For more information, consult the FDA publication, Grapefruit Juice and Medicine May Not Mix.

– Pamela S

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