Grapefruit juice makes cancer drugs more effective

A glass daily increases the content of the drug in the blood by up to 350 percent

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Grapefruit juice can make some anticancer drugs more effective. Because the fruit juice inhibits enzymes in the intestine, which normally break down these medicines. This keeps the agent longer in the body and requires a lower dose to achieve the same effect. This shows a study of American researchers with 138 cancer patients. They had studied the effect of grapefruit juice on the agent sirolimus. This substance, also known as rapamycin, has long been used to cushion the immune system during transplantation, but it also works against cancerous tumors according to the latest findings.

A mere quarter liter of grapefruit juice has increased the amount of sirolimus in the blood of these patients by up to 350 percent, the researchers report in the journal "Clinical Cancer Research". In order to get the most effective blood value of the drug, these patients needed only 25 to 35 milligrams of sirolimus per week instead of the otherwise needed 90 milligrams.

"This is the first cancer study to investigate this food-drug interaction, " study director Ezra Cohen of the University of Chicago and his colleagues write. It shows that a non-toxic food available in every supermarket can significantly improve the bioavailability of some medicines.

Sirolimus is a substance that inhibits the proliferation of cells and can therefore also slow down the growth of tumors. For some cancers, including Kaposi's sarcoma and liver cell cancer, this has been shown in studies, the researchers explain. Some of the sirolimus-related chemicals are also used against kidney cancer and some tumors of the nervous system. These drugs are broken down in the body by certain enzymes, the so-called p70-S6 kinases. The funds must therefore be relatively high doses to compensate for this ongoing depletion.

According to the researchers, the fruit juice effect now identified could help reduce the dose of sirolimus and related remedies in the future. This saved the patient many harmful side effects. At the same time, however, this makes the treatments significantly cheaper. Such results are not exactly profitable for the pharmaceutical industry, the researchers comment. This also explains why they rarely carry out or promote studies looking for ways to lower doses. display

Cancer drugs with and without fruit juice

For their study, the researchers divided 138 patients with incurable end-stage cancer into three groups. One received twice weekly only the tumor-inhibiting sirolimus. The second group of patients took the remedy plus a quarter liter of grapefruit juice, the third sirolimus and additionally ketoconazole, a chemical that also inhibits the degrading enzymes. In all groups, the scientists slowly increased the dosage of the anticancer agent until it reached the optimal effective concentration in the patient's blood.

Patients taking only sirolimus needed 90 milligrams per week to get the most effective blood counts, the researchers report. Patients who also drank grapefruit juice needed only 25 to 35 milligrams of the drug. The fruit juice has increased the concentration of the cancer drug in their blood by up to 350 percent, write Cohen and his colleagues. In the ketoconazole group, only 16 milligrams of the anticancer drug were needed. Although this chemical has a slightly stronger effect than the fruit juice. The advantage of the juice, however, is that it is not toxic and can not cause an overdose. (Doi: 10.1158 / 1078-0432.CCR-12-0110)

(Clinical Cancer Research, 08.08.2012 - NPO)