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 prescribed. They also showed that the combination can be effective in treating various types of cancer.
This is interesting information, because it now appears that studies are ongoing to take advantage of the drug interaction that occurs with grapefruit. For twenty years, pharmacists have pasted "DO NOT TAKE WITH GRAPEFRUIT JUICE" stickers on various pill bottles because the juice can interfere with the enzymes that break down and eliminate certain drugs. This interference has always been considered dangerous, because It can make the drugs more potent.
However, in data presented at the AACR 100th Annual Meeting in Denver last week, the Chicago researchers examine ways to exploit this fruit's medication-altering properties. They have identified a drug that can be reduced to much lower dosage levels when combined with this citrus juice.
"Grapefruit juice can increase blood levels of certain drugs by 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."
The clinical trial was designed to test whether doctors could use grapefruit juice to boost rapamycin's bioavailability to the patient's advantage -- to determine how much the juice altered drug levels, and then to assess its impact on anti-cancer activity and side effects.
Cancer specialists became interested in rapamycin when they learned that it disrupted a biochemical pathway involved in the development of the new blood vessels that tumors need to grow. But the drug is so expensive, and so poorly absorbed. Less than 15 percent of rapamycin goes to work in the body when taken by mouth.
That's why it is great that substances known a furanocoumarins, plentiful in grapefruit juice, can decrease the breakdown of rapamycin. This makes the drug reach higher levels in the bloodstream; in fact, two-to-four times the levels seen without a juice boost, and thus increases the amount of the drug that reaches its targets.
"That means more of the drug hits the target, so we need less of the drug," said Cohen. And when a drug like this is so expensive, that has a very serious bottom line benefit to all. "This is an opportunity for real savings," Cohen said. "A daily glass of juice could lower the cost by 50 percent."