TUESDAY, Aug. 7 (HealthDay News) -- In a small study of patients with incurable cancer, drinking 8 ounces of grapefruit juice a day boosted the effect of a drug they were given during the study.
Although some participants had a response, tumors did not disappear after using the drug, which is mostly used to treat conditions unrelated to cancer. The study's main finding was that grapefruit juice might allow treatment using smaller drug dosages, therefore reducing side effects and perhaps costs.
Sirolimus (Rapamune) is an immunosuppressant and not approved as a cancer drug. Its primary use is to prevent rejection after kidney transplants. It is also used as a treatment for psoriasis, the researchers noted.
Some early studies suggest that sirolimus may have tumor-fighting effects. Derivatives of the drug are used in kidney cancer and breast cancer.
The drug, however, has what is called poor bioavailability, which means the body can't use it efficiently. Only about 14 percent of it gets absorbed, said lead researcher Dr. Ezra Cohen, assistant professor of medicine at the University of Chicago Medical Center.
"We thought if we could manipulate it we could increase the availability, make it easier to take and make it more effective," Cohen said.
With grapefruit juice or another drug, the researchers were able to increase the effectiveness and also lower the dose of sirolimus, he said.
"This has a wider application beyond sirolimus," Cohen said. "This is a proof of principle that grapefruit juice could be used in this way."
Cohen said this same tactic will work with other cancer drugs and could dramatically reduce costs.
"Cancer drugs that are being introduced will cost anywhere from $3,000 to $10,000 per month," he said. "Here's a mechanism that might allow us to significantly reduce the cost."
For example, sirolimus costs about $1,000 a
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