Although a drug called sirolimus (brand name Rapamune) is approved for suppressing the immune system in patients with kidney transplants, it is often used off-label for treating advanced cancer patients. The trouble, though, is that the drug is not particularly "bioavailable," meaning that the body doesn't use it very efficiently.
However a recent study published in the journal Clinical Cancer Research showed that combining sirolimus with plain old grapefruit juice upped the med's effectiveness almost as much as a combining it with a drug called ketoconazole (brand name: Nizoral.) As a result, patients' doses of sirolimus could be reduced, and side effects lessened. The advantage of grapefruit juice over ketoconazole, according to MedPage Today, is that it is not toxic and carries no risk of overdose. Grapefruit juice works by inhibiting enzymes in the intestine that break down sirolimus.
Lead researcher Dr. Ezra Cohen, assistant professor of medicine at the University of Chicago Medical Center, told MedPage Today, "We thought if we could manipulate [sirolimus] we could increase the availability, make it easier to take and make it more effective . . .This has a wider application beyond sirolimus. This is a proof of principle that grapefruit juice could be used in this way . . . Cancer drugs that are being introduced will cost anywhere from $3,000 to $10,000 per month," he said. "Here's a mechanism that might allow us to significantly reduce the cost."
