In a small, early clinical trial, researchers at the University of Chicago Medical Center have found that combining eight ounces of grapefruit juice with the drug rapamycin can increase drug levels, allowing lower doses of the drug to be given.
They also showed that the combination can be effective in treating various types of cancer.
For two decades, pharmacists have pasted DO-NOT-TAKE-WITH-GRAPEFRUIT-JUICE stickers on various pill bottles because it can interfere with the enzymes that break down and eliminate certain drugs. This interference makes the drugs more potent. In data presented at the AACR 100th Annual Meeting 2009, the Chicago researchers examine ways to exploit this fruit's medication-altering properties.
"Grapefruit juice can increase blood levels of certain drugs three to five times," said study director Ezra Cohen, MD, a cancer specialist at the University of Chicago Medical Center. "This has always been considered a hazard. We wanted to see if, and how much, it could amplify the availability, and perhaps the efficacy of rapamycin, a drug with promise for cancer treatment."
This trial was designed to test "whether we could use this to boost rapamycin's bioavailability to the patient's advantage, to determine how much the juice altered drug levels, and to assess its impact on anti-cancer activity and side effects," he said.
The study followed 28 patients with advanced solid tumors, for which there is no effective treatment. The dose of the drug increased with each group of five patients, from 15 milligrams up to 35. Patients took the drug by mouth, as a liquid, once a week.
Beginning in week two, they washed it down with a glass of grapefruit juice ( Citius paradisi ), taken immediately after the rapamycin and then once a day for the rest of the week.
Twenty-five participants remained in the study long enough to be evaluated. Seven of those 25 (28%) had stable disease, with little or no tumor growth. One patient (4%) had a partial response, with the tumor shrinking by about 30 percent. That patient is still doing well more than a year after beginning the trial.
"My first cancer doctor gave me five years to live," said that patient, Albina Duggan of Bourbonnais, IL. "That time runs out next July."
Duggan, mother of four, has a rare cancer, an epitheliod hemangioendothelioma that originated in the liver and subsequently spread to two vertebrae in the neck and to the lymph nodes. She had surgery and radiation therapy and was evaluated for a liver transplant, but evidence of cancer beyond the liver made her ineligible for a transplant. She "shopped around" for other therapies and was able to keep the disease in check for a year with sorafenib, a drug approved for kidney and liver cancers.
After a year of stable disease, however, her tumor began growing again and she had to look for an alternative therapy. Her doctors at the University of Chicago offered three clinical trials. The most appealing to her was the rapamycin plus grapefruit juice study. She took her first dose March 11, 2008, and is still on the drug-juice combination.
"My tumor is smaller and it's no longer growing. I feel fine. I can do whatever I like and I have no real side effects," she said. "What's not to like?"