Grapefruit may make more drugs deadly

Canadian scientists say the number of common prescription drugs that can interact badly with grapefruit is climbing, with the potential for dangerous, even deadly, results.

Twenty-six new drugs that can cause serious harm when mixed with grapefruit have been introduced in the past four years alone, bringing the total to 43, said Dr. David Bailey, a clinical pharmacologist at the Lawson Health Institute Research Center in London, Ontario. That’s an average of more than six new drugs a year.

“What I’ve seen has been disturbing,” said Bailey, lead author on a study published in the Canadian Medical Association Journal. “It’s hard to avoid putting a drug out on the market that is not affected by grapefruit juice.”

Click here to see a complete list of drugs than can interact with grapefruit.

The trouble with grapefruit has been known for two decades, ever since Bailey and his colleagues first discovered that ingestion of the fruit with certain prescription drugs can concentrate the medication in a patient’s bloodstream. And it doesn’t matter whether the grapefruit is consumed hours before the pills, the researchers found.

The problem is caused by an active ingredient in some citrus fruits, including grapefruit, limes and pomelos. Even the Seville oranges used in marmalades can trigger it. The fruits produce organic chemical compounds called furanocoumarins, which interfere with a human digestive enzyme.

Officials there say that although some drugs do interact with grapefruit, most do not. In most cases, doctors can prescribe drugs in the same class that don’t interact, noted Karen Mathis, a Florida Department of Citrus spokeswoman.

And not all citrus poses a problem, Bailey noted. Sweet oranges, such as navel and Valencia varieties, don’t contain the damaging compound.