Grapefruit Juice Boosts Effect Of Common Cancer Fighting Drug
August 8, 2012

Grapefruit Juice Boosts Effect Of Common Cancer Fighting Drug

Connie K. Ho for — Your Universe Online

There´s the saying, “An apple a day, keeps the doctor away.” For cancer patients, it might be lucrative to drink grapefruit juice instead.

According to a new clinical trial, drinking a glass of grapefruit juice a day allows patients to have the same benefits as the effect produced from three times of an anti-cancer drug. The researchers believe that the grapefruit juice could help patients take smaller amounts of the anti-cancer drug, thus lessening negative side affects and decreasing the cost of the medication.

The study, published in the August issue of Clinical Cancer Research, was conducted by researchers from the University of Chicago Medicine who looked at the impact that different foods have on the uptake and elimination of drugs utilized for cancer treatment. They found that drinking eight ounces a day of grapefruit juice could help slow the body´s metabolism of sirolimus, a drug approved for transplant patients but also for those who are diagnosed with cancer. Those who consumed eight ounces of grapefruit juice a day boosted their sirolimus levels by 350 percent. Another drug, ketoconazole, could also slow the drug´s metabolism and pump up the sirolimus levels by 500 percent.

"Grapefruit juice, and drugs with a similar mechanism, can significantly increase blood levels of many drugs," explained study director Dr. Ezra Cohen, a cancer specialist at the University of Chicago Medicine, in a prepared statement. "But this has long been considered an overdose hazard. Instead, we wanted to see if grapefruit juice can be used in a controlled fashion to increase the availability and efficacy of sirolimus."

The project consisted of three simultaneous phase-1 trials of sirolimus where patients received only sirolimus, siroliumus and ketoconazle, or sirolimus and grapefruit juice. A total of 138 patients with incurable cancer participated in the study. The investigators discovered that the optimum amount for those only taking sirolimus to fight cancer was approximately 90 mg per week; any doses that were above 45 mg also had side effects like nausea and diarrhea. For those who were taking sirolimus with ketoconazole, they only needed 16 mg per week to have the same drug levels in their blood stream. Those who took sirolimus with grapefruit juice, only needed from 25 to 35 mg of sirolimus per week.

Through the study´s findings, the researchers believe that the powerful effect of grapefruit juice is due to its power to stop enzymes in intestines that normally break down sirolimus and other drugs. The influence of grapefruit juice on the body is seen in the beginning, when the individual first consumes the liquid, and it lasts for a few days.

"This is the first cancer study to harness this drug-food interaction," the authors remarked in the statement.

With grapefruit juice, the participants had a higher chance of not risking drug overdose.

"”We have at our disposal an agent that can markedly increase bioavailability (in this study by approximately 350%) and, critically in the current environment, decrease prescription drug spending on many agents metabolized by P450 enzymes,” wrote the authors in the statement.

Even though the impact of grape fruit juice for patients may vary based on the number of enzymes that are produced to break down sirolimus, the level of the enzymes can help estimate the response of an individual participant.

"The variation in potency of the grapefruit juice itself may be far greater than the variation in the enzymes that break down sirolimus," Cohen concluded in the statement.