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Grapefruit juice, long known to have dangerous interactions with numerous prescription medications, appears to actually improve the use of a promising cancer drug.
Researchers at University of Chicago Medicine found that a glass of grapefruit juice so improved the body's uptake of a potent drug called sirolimus that they could cut the drug dosage by a third to reach the same desired effect as a full dose.
The lower dose meant that patients had far fewer side effects from the drug. If this same mechanism can work on similar drugs — something the researchers say is hopeful — doctors could prescribe other medications at lower doses, reducing side effects and saving money.
The study is reported today (Aug. 7) in the journal Clinical Cancer Research.
Fruit-drug cocktails
The researchers, led by Ezra Cohen, a cancer specialist at the University of Chicago Medicine, harnessed the same pharmacological properties that make grapefruit juice so menacing when taken with prescription drugs. [Top 10 Cancer-Fighting Foods]
Grapefruit juice inhibits certain enzymes in the intestinal walls that otherwise would slow many drugs from entering the bloodstream. With the enzymes blocked, these drugs move more quickly and freely into the bloodstream and can spike the body with dangerous and even toxic levels of the medication.
These drugs include cholesterol-lowering statins, many psychiatric drugs such as Valium and Zoloft, pain medications such as methadone, and many more, including sirolimus.
Sirolimus, also called rapamycin, was originally used as an antifungal medication. After the drug was also found to be a powerful immunosuppressant, it was used to prevent rejections in organ transplants, especially kidney transplants.
More recently, sirolimus has been shown to slow the spread of certain cancers, particularly incurable brain and blood cancers.
Grapefruit chaser
As with many powerful drugs, sirolimus has its side effects. At doses above 45 mg per week, the Chicago researchers said, the drug causes serious gastrointestinal problems, such as nausea and diarrhea, so bad that patients have to be rotated to lower doses.
Cohen's group conducted a study on 138 people with incurable cancers to determine an ideal dose. A third received only sirolimus; a third took sirolimus with 8 ounces of grapefruit juice; and a third took sirolimus with another drug, called ketoconazole, which also increases sirolimus' absorption.
The researchers found that the optimal cancer-fighting dose for those taking only sirolimus was about 90 mg per week, twice as high as the side-effect threshold. Those drinking grapefruit juice, however, needed only about 25 to 35 mg per week of sirolimus.
Those patients on ketoconazole needed only 16 mg per week of sirolimus, the study found. But Cohen said that grapefruit juice was superior in that it is natural and non-toxic … and cheaper.
"We have at our disposal an agent that can markedly increase bioavailability (in this study by approximately 350 percent) and … decrease prescription drug spending on many agents metabolized by P450 enzymes," those gut enzymes that grapefruit juice blocks, the authors wrote in their report.
Cohen said that one drawback is predicting the effect of grapefruit juice. Note the precise dosage determined with the use of ketoconazole, 16 mg, compared with the range with grapefruit juice. This may be due to the juice formulation, which is less precise than that of a pharmaceutical drug.
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2 Comments
Add CommentI love grapefruit juice,but can't drink it because of harmful drug interaction with my cardiac meds.
Reply | Report Abuse | Link to thisThis kind of an article should never have been published in a general audience magazine. It's known from long time ago that Grapefruit juice inhibits some CYPs, or Cytochrome enzyme systems that participate in the transformation of drugs inside the body, but there's a lot of interpersonal variation in these metabolic systems or pathways, and something that can work well in somebody can be dangerous for others. Drug makers do establish an standard way for taking drugs, as for example, local, cultural and seasonal variations in the things people eat can greatly influence the extent of drug's absorption and metabolism, thus influencing its therapeutic activity. There are some targeted drugs for cancer for which the pharmaceutical company advises taking it with an empty stomach, when it's known that the same drug taken with some kinds of a meal will have a nearly doubled absorption from the gut, and thus the same blood therapeutic concentrations could be achieved with half the amount of drug per dosing, and these are expensive drugs. The issue is that neither the quality and components of meals are equal from person to person or from day to day, nor the condition of guts is stable, nor anybody from the pharmaceutical company to even your doctor are fully sure of the rest of concomitant drugs or products the patient is taking, and there are so many possible combinations of drug-drug, drug-person, drug-food, drug-herbal or alternative medicine products interactions and so on, that it's impossible testing them all to issue comprehensive instructions for every patient under any situation. It has been shown that the use of alternative medicines and herbal products in patients receiving chemotherapy for cancer does reduce the patient's Relapse Free Survival, patients on chemotherapy plus alternative medicine products relapse earlier than those only on chemotherapy, and Overall Survival, those receiving only chemotherapy live longer than those on chemotherapy plus herbal or alternative medicine products, so it's an extremely dangerous behavior playing the bartender and preparing cocktails with drugs, juices and any other stuff, savings in medical therapy have a higher involved cost, even at short term, and are almost universally harmful to the patients. Please forget about any kind of juices mixing with anticancer drugs, package inserts and websites with information for patients are there to be read before taking any drug or medical product. Salut +
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