... At the University of Chicago, scientists are studying grapefruit juice in combination with an experimental anticancer compound, hoping to boost the drug's weak effects. In Florida, Bioavailability Systems LLC, a small biotechnology company, claims to have purified the grapefruit compounds responsible for the boosting effect and has been able to improve the blood levels of an anti-HIV drug. "This is definitely a lemons to lemonade story," says James Harris, founder and chief scientific officer of the company.
The approach aims to tackle a major problem for drug manufacturers: the great degree of variation in how people absorb drugs. Partly to blame is the fact that individuals have different levels of an enzyme in the intestines and liver, called CYP3A4, that breaks down drugs before they even have the chance to get into the bloodstream. People with very active CYP3A4 get lower amounts of drugs into their systems than those with low levels of the enzyme.
But powerful compounds in the grapefruit called furanocoumarins obliterate CYP3A4 in the gut. The result: More drug gets into the bloodstream. For some anticholesterol statins, for example, taking one tablet with a glass of grapefruit juice "is like taking at least 10 tablets with a glass of water," says David Bailey, a pharmacologist at the University of Western Ontario who discovered the grapefruit effect in the early 1990s. It's why some major blockbusters, like the statin Mevacor or the anticancer drug Gleevec, contain warnings against taking these drugs with grapefruit juice.
But for certain drugs that have a hard time reaching optimal blood levels at prescribed doses, some doctors are interested in intentionally boosting the effects with grapefruit. Generally, the idea would be to give a booster to all patients who are taking a weak drug. While some patients may have naturally low levels of the CYP3A4 enzyme and thus wouldn't need it, there's no practical way to test individuals right now, so researchers are using a blanket approach. As long as a drug does not have what is known as a "narrow therapeutic window" -- meaning that a relatively small increase in dose makes it toxic -- boosting shouldn't necessarily lead to large increases in side effects, the theory goes. ...
onder:
