Alert: Mixing Grapefruit with Certain Medications can be Deadly


Editor’s note: We all sort of know this about grapefruit, but a recent study shows that we need to be more aware than we have been.



Grapefruit lovers beware: Mixing the tart citrus with certain drugs can be deadly, according to a new study published Monday in the Canadian Medical Association Journal. There are 84 drugs that interact 1) ___ with grapefruit in its various forms, even when patients don’t consume much of it, according to this recent study. It was also found that the number of common prescription drugs that can cause dangerous interactions with grapefruit is 2) ___.


Twenty-six new drugs that can cause serious 3) ___ 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. “It’s hard to avoid putting a 4) ___ out on the market that is not affected by grapefruit juice.” However, not all have serious consequences. Those that do, however, can cause problems, such as acute kidney failure, respiratory failure, gastric bleeding and worse. For example, the heart drug dronedarone, or Multaq, has a very high risk of interaction when taken with grapefruit, which may cause a rare form of ventricular tachycardia or rapid 5) ___ rhythm. Another example is mixing grapefruit with the prescription painkiller 6) ___ which can cause serious breathing problems. Also, adding grapefruit to a dose of the popular statin simvastatin, or Zocor, can lead to rhabdomyolysis, a breakdown of muscle fibers that can lead to kidney damage.


The problem with mixing grapefruit and some medications 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 7) ___ in a patient’s bloodstream.


Drinking less than a cup of grapefruit juice once a day for three days, for instance, can lead to a 330% concentration of simvastatin. And it doesn’t matter whether the 8) ___ is consumed hours before the pills. 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. That enzyme, called CYP3A4, helps metabolize toxic substances to keep them from getting into the 9) ___. Typically, that means the enzyme inactivates the effects of about 50% of all medications. Doctors can, theoretically, adjust for that when prescribing drugs.


However, when the furanocoumarins in citrus inhibit that enzyme, the drugs can become concentrated in a patient’s system. In some cases, it can be like getting a triple or quadruple dose of medication. Drugs known to interact with grapefruit do carry warnings, but Bailey said he believes that neither doctors nor patients may take the threat seriously enough. “Basically, most people are sort of aware of grapefruit juice drug interactions, but I don’t think it’s in the forefront of their mind on a regular basis,” he said. It’s not clear how many people actually are harmed by grapefruit interactions, mostly because the side 10) ___ are often not recognized as being related to the citrus, said Bailey, who included eight case reports in his study. Part of the concern lies in the fact that people older than 45 are most likely to consume grapefruit juice — and to take prescription drugs. Seniors older than 70 years of age have the most trouble tolerating excessively high levels of drugs.


Patients worried about the interaction of grapefruit with their medications should talk with their doctors, Bailey said. And doctors should make sure to ask about grapefruit consumption when prescribing drugs.


Some grapefruit lovers may have cut back already because of the risk of drug 11) ___. Consumption of grapefruit juice has dropped in the past decade, falling from .44 gallons of juice per person per year in 2000 to 0.15 gallons per person in 2011, according to figures from the Florida Department of Citrus. 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 department spokeswoman. “These medications often can provide the same therapeutic effect with no need to avoid grapefruit juice,” she said in a statement. And not all citrus poses a problem, Bailey noted. Sweet oranges, such as navel and Valencia varieties, don’t contain the damaging compound. “You have an alternative there,” he suggested. “If you want to take your medications with 12) ___ juice, you’re home free.”


ANSWERS: 1) negatively; 2) rising; 3) harm; 4) drug; 5) heart; 6) oxycodone; 7) medication; 8) grapefruit; 9) bloodstream; 10) effects; 11) interaction; 12) orange


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