Health & Medicine
Grapefruit Juice May Boost Cancer Treatment: Study
Brooke Miller
First Posted: Aug 08, 2012 06:27 AM EDT
For years doctors have warned their patients about drug interactions with grapefruit juice that could be dangerous for them, but it appears that this tart drink actually improves the use of a promising cancer drug by interacting with the drugs in a positive way, reducing dosages, cost and side effects.
According to a new clinical trial, "A glass a day of grapefruit juice lets patients derive the same benefits from an anti-cancer drug as they would from more than three times as much of the drug by itself."
Grapefruit juice is known to increase the levels of a particular drug known as sirolimus in the patient's blood. This potent drug could cut the dosage by a third to reach the same desired effect as a full dose.
Researchers at the University of Chicago wished to test the effectiveness of the drug. Dr. Ezra Cohen, assistant professor of Medicine at the University of Chicago Medical Center and his colleagues tested sirolimus, a transplant drug, with anti-cancer effects in 138 patients with incurable cancer.
The researchers noticed that combining sirolimus with grapefruit juice caused the blood levels to rise potentially with relatively few side effects.
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 study was published in Monday's online issue of Clinical Cancer Research.
Explaining further about sirolimus, Dr. Cohen said, "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. We thought if we could manipulate it we could increase the availability, make it easier to take and make it more effective. With grapefruit juice or another drug, the researchers were able to increase the effectiveness and also lower the dose of sirolimus. This has a wider application beyond sirolimus. This is a proof of principle that grapefruit juice could be used in this way."
According to the study, for patients taking sirolimus alone, their optimal dose was 90 milligrams per week. However, the patients also suffered from serious gastrointestinal problems when they took more than 45 mg of sirolimus per week, so they had to switch to 45 mg twice a week. Those who were taking ketoconazole in conjunction with sirolimus only needed 16 mg of sirolimus to maintain optimal levels of the anti-cancer drug in their blood. Patients drinking grapefruit juice needed just between 25 and 36 mg of sirolimus weekly.
While ketoconazole was more effective, researchers recommend the more naturally-derived grapefruit juice, as it was a much less-toxic option. Ultimately, the juice works by slowing the cancer drug's metabolism.
The researcher hopes that this study encourages further research on the effects of herbal and natural compounds in combination with cancer therapy, as well as takes a closer look at what sirolimus can do.
Cohen concluded by saying, "The simple way to think about it is that grapefruit juice inhibits the production of the enzymes by the cells that line our gut. There's no direct effect on the drug, instead it inhibits the enzymes that metabolize the drug. We're realizing with these drugs, they do work very well in certain combinations, so there may be more and more approval for this class of drug."
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First Posted: Aug 08, 2012 06:27 AM EDT
For years doctors have warned their patients about drug interactions with grapefruit juice that could be dangerous for them, but it appears that this tart drink actually improves the use of a promising cancer drug by interacting with the drugs in a positive way, reducing dosages, cost and side effects.
According to a new clinical trial, "A glass a day of grapefruit juice lets patients derive the same benefits from an anti-cancer drug as they would from more than three times as much of the drug by itself."
Grapefruit juice is known to increase the levels of a particular drug known as sirolimus in the patient's blood. This potent drug could cut the dosage by a third to reach the same desired effect as a full dose.
Researchers at the University of Chicago wished to test the effectiveness of the drug. Dr. Ezra Cohen, assistant professor of Medicine at the University of Chicago Medical Center and his colleagues tested sirolimus, a transplant drug, with anti-cancer effects in 138 patients with incurable cancer.
The researchers noticed that combining sirolimus with grapefruit juice caused the blood levels to rise potentially with relatively few side effects.
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 study was published in Monday's online issue of Clinical Cancer Research.
Explaining further about sirolimus, Dr. Cohen said, "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. We thought if we could manipulate it we could increase the availability, make it easier to take and make it more effective. With grapefruit juice or another drug, the researchers were able to increase the effectiveness and also lower the dose of sirolimus. This has a wider application beyond sirolimus. This is a proof of principle that grapefruit juice could be used in this way."
According to the study, for patients taking sirolimus alone, their optimal dose was 90 milligrams per week. However, the patients also suffered from serious gastrointestinal problems when they took more than 45 mg of sirolimus per week, so they had to switch to 45 mg twice a week. Those who were taking ketoconazole in conjunction with sirolimus only needed 16 mg of sirolimus to maintain optimal levels of the anti-cancer drug in their blood. Patients drinking grapefruit juice needed just between 25 and 36 mg of sirolimus weekly.
While ketoconazole was more effective, researchers recommend the more naturally-derived grapefruit juice, as it was a much less-toxic option. Ultimately, the juice works by slowing the cancer drug's metabolism.
The researcher hopes that this study encourages further research on the effects of herbal and natural compounds in combination with cancer therapy, as well as takes a closer look at what sirolimus can do.
Cohen concluded by saying, "The simple way to think about it is that grapefruit juice inhibits the production of the enzymes by the cells that line our gut. There's no direct effect on the drug, instead it inhibits the enzymes that metabolize the drug. We're realizing with these drugs, they do work very well in certain combinations, so there may be more and more approval for this class of drug."
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone