A small amount of grapefruit, even ingested hours before taking the medications, can increase the amount of the drug metabolized, which is like taking many doses at once, the researchers said.
The toxic effect can build when the drug is taken repeatedly. For example, if the cholesterol-lowering drug Zocor is combined with a 7-ounce glass of grapefruit juice once a day for three days, the drug in the bloodstream will increase 330 percent, Bailey said.
According to the report, drugs that can interact with grapefruit include:
Because people older than 45 are the major buyers of grapefruit and are more likely than younger individuals to take a variety of medications, they are most at risk. Also, because of their advanced age, they are most vulnerable to the harmful reactions of grapefruit-drug combinations, the researchers said.
Dr. Gregg Fonarow, a spokesman for the American Heart Association and a professor of cardiology at the University of California, Los Angeles, said little is known about how often these adverse effects occur in real world practice. Further studies are necessary, he added.
"Patients taking medications where there are potentially serious adverse interactions should, in general, be advised to avoid consumption of moderate or large quantities of grapefruit, or together with their physician consider potential alternative medications that are not metabolized by the liver enzyme inhibited by grapefruit," Fonarow said.'/>"/>
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