Grapefruit juice helps boost cancer drug, U. of C. study finds - Chicago Sun

Doctors at the University of Chicago have found that eight ounces of grapefruit juice a day helps certain cancer patients by helping absorption of a cancer-fighting drug.

Only a tiny amount of the drug — sirolimus — is normally absorbed into the bloodstream. And giving patients more of the drug would be costly and worsen side-effects, including nausea and diarrhea.

So the doctors looked for a way to boost absorption of the drug and landed on grapefruit juice — which can cause overdoses when drunk with a range of drugs, including cholesterol drugs and antihistamines, but which helped in this case, making it possible to give less of the drug and cut costs.

In a small study of nearly 150 patients with incurable cancer, the researchers found that sirolimus did not make patients' tumors disappear, but about 30 percent of the patients did see their tumor stabilize for a while, according to a report this week in the journal Clinical Cancer Research..

Sirolimus, which is an immunosuppressant, is not approved for treatment of cancer. Its primary use is to prevent rejection after kidney transplants. But some early studies suggest that sirolimus might have tumor-fighting effects, said lead researcher Dr. Ezra E.W. Cohen, associate professor of medicine at the University of Chicago Medical Center.

Only a small percentage of sirolimus —14 percent — is absorbed into the bloodstream. In the study, patients were given sirolimus alone, sirolimus plus grapefruit juice or the drug along with ketoconazole, which is used to treat fungal infections.

With grapefruit juice, the researchers were able to increase sirolimus levels by 350 percent and lowered the doses from 90 milligrams a week to between 25 and 35 mg a week.

Ketoconazole also increased sirolimus levels by 500 percent, the study found. But unlike grapefruit juice, it has side effects.

Grapefruit juice inhibits enzymes in the intestine that break down sirolimus and several other drugs.

Cohen noted that not all grapefruit juice is the same and some types don't have enough of the active ingredient to have an effect on drugs. And because the study was only a preliminary trial, people should not use grapefruit juice for this purpose until more studies have been done, he cautioned.

Cohen estimated that the reduction in the sirolimus dosage could cut pricing from $1,000 a month to about $400.

Grapefruit juice potentially could be used the same way with other oral drugs that affect other cancers, he said.

"We really see this as a way to dramatically reduce health-care costs," Cohen said.