The idea behind grapefruit juice enhancing effects, is that grapefruit juices contain an MAOI, a monoanimeoxidase inhibitor. There are Rx labels that come with drugs like narcotic pain killers that stress not to take the Rx drug while or after drinking grapefruit juice. this was found after 2 minutes of googlin;
Compounds in grapefruit juice inhibits an enzyme required for metabolism of nearly half of prescription drugs on the market. If you inhibit drug metabolism, would that allow you to take a lower (and cheaper) dose of one of those drugs, especially an expensive drug?
That is the proposition of a company called Bioavailability Systems, featured in today's Wall Street Journal and alluded to on the WSJ Health Blog (yes, I cite the WSJ very often but only because they have some of the best medical and health reporting on topics well ahead of the MSM curve).
The intestines and the liver contain many drug metabolizing enzymes but the one in question here is a cytochrome P450 monooxygenase called CYP3A4. The enzyme works on drug molecules to slap on a water-soluble chemical group or remove water-insoluble groups. In most (but not all) cases, this action terminates the biological action of the drug.
In 1991, David Bailey and colleagues at the University of Western Ontario reported in The Lancet that grapefruit juice was found to increase blood levels of felodipine, a calcium channel-blocking antihypertensive drug. The precise reason was that grapefruit juice inhibited the CYP3A4 enzyme, an effect that was later ascribed to a group of compounds called furanocoumarins (bergamottin and 6',7'-dihydroxybergamottin). So, taking felodipine while drinking grapefruit juice was essentially the same as taking a higher dose of the drug because its elimination from the body was slowed. Today's WSJ article and blog post discuss the experimental and commercial approach to using CYP3A4 inhibitors as "dose boosters" to minimize the dose one needs to take of some very expensive drugs.
