Grapefruit Drug Interactions: Fruit Reacts Dangerously With Expanding List Of Medications, Study Says

While eating a grapefruit or drinking its juice may be an excellent way to get a delicious, tangy dose of vitamin C, doctors now warn that the citrus fruit may prove hazardous when combined with certain prescription drugs.

Although the combination of grapefruit and certain medications has long been known to cause problems, a new study by a team of Canadian researchers has revealed that the number of these drugs has increased throughout the years.

"The number of drugs on the market with the potential to produce serious adverse and in many cases life-threatening effects when combined with grapefruit has markedly increased over the past few years from 17 to 43 in four years," said lead researcher David Bailey, from the Lawson Health Research Institute in Ontario, Canada, according to HealthDay.

Bailey added that a total of more than 85 drugs on the market may interact in some way with grapefruit.

Many of the drugs are common, such as some cholesterol-lowering statins, antibiotics and calcium channel blockers used to treat high blood pressure. Others include agents used to fight cancer or suppress the immune system in people who've received an organ transplant.

People older than 45 buy the most grapefruit and take the most prescription drugs, making this group the most likely to face interactions, researchers said.

"Half of these drugs actually can cause sudden death," Bailey said, adding that interactions may also result in "acute kidney or respiratory failure, gastrointestinal bleeding, or other serious effects," according to the Ottawa Citizen.

As HealthDay reports, even small amounts of grapefruit or its juice have the potential to cause serious problems.

"One tablet with a glass of grapefruit juice can be like taking five or 10 tablets with a glass of water and people say I don't believe it, but I can show you that scientifically it is sound," Bailey told the BBC. "So you can unintentionally go from a therapeutic level to a toxic level just by consuming grapefruit juice."

The hazardous interactions can also occur many hours after grapefruit is consumed, CBC reports. Even if someone eats grapefruit or drinks the juice "hours before taking a drug, such as downing the drink at breakfast and taking the medication after dinner," an interaction can still occur.

In the new report, published Monday in the Canadian Medical Association Journal, Bailey and his team also warn against a general "lack of knowledge" about the dangers of mixing certain medications with grapefruit.

"We contend that there remains a lack of knowledge about this interaction in the general health care community," the report said, according to the BBC. "Unless health care professionals are aware of the possibility that the adverse event they are seeing might have an origin in the recent addition of grapefruit to the patient's diet, it is very unlikely that they will investigate it."

According to the Ottawa Citizen, some of the drugs that may interact badly with grapefruit include a number of commonly prescribed statins like atorvastatin (Lipitor), simvastatin (Zocor) and lovastatin (Mevacor, Altoprev).

The newspaper adds that the anti-clotting agent clopidogrel (Plavix), which is taken to prevent a heart attack or stroke, doesn't work "at all" if grapefruit is taken with it.

As the BBC notes, grapefruits are not the only fruit that can interact with these medications. Other citrus fruits such as Seville oranges and limes reportedly have the same effect.

Of course, with grapefruit's antioxidant properties and excellent nutritional goodness, people shouldn't run a mile from the juicy fruit if they don't need to. Still, patients should always read the label and warnings of prescription medications before taking them.

For more information on drug interactions, visit the U.S. National Library of Medicine.

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