Study Warns of Deadly Grapefruit Drug Interactions

grapefruit drug interaction

A glass of grapefruit juice may sound like the perfect complement to a healthy breakfast or lunch. The juice is well-known to be high in Vitamin C, in addition to being a good source of antioxidants. Overall, grapefruit juice is indeed a very healthy part of a good diet – as long as you’re not taking one of dozens of medications that could lead to dangerous or even deadly grapefruit drug interactions.

According to a new study conducted at London, Ontario’s Lawson Health Research Institute, 26 drugs have been newly discovered to interact dangerously with grapefruit in the last four years. Previous studies had already identified 17 drugs that could cause serious harm when mixed with grapefruit. A total of 85 drugs are now known to have at least some interaction with grapefruit, though not all of these interactions pose significant danger.

Sudden Death is Possible with Some Grapefruit Drug Interactions

Clinical psychologist Dr. David Bailey, one of the lead researchers behind the study, said that it’s becoming difficult to bring a drug to market that doesn’t interact with grapefruit. According to Bailey, these interactions can occur in the presence of fresh grapefruit juice, grapefruit concentrate and whole grapefruit. These interactions can be extremely dangerous, and include gastric bleeding, respiratory failure, kidney failure and even death.

Bailey said that a total of 13 drugs can be fatal when combined with grapefruit, and that it wouldn’t be sensational to describe the interaction as sudden death. One such drug is dronedarone, a heart drug commonly known as Multaq, which can cause rapid heart rhythm or ventricular tachycardia when combined with grapefruit.

Another drug known to interact dangerously with grapefruit is oxycodone, a prescription painkiller known for its high risk of abuse. When mixed with grapefruit, oxycodone can create significant respiratory problems. Another popular drug, Zocor, can cause a breakdown in muscle tissue and kidney damage.

A full list of all drugs that interact with grapefruit, including medications designed to treat cancer, diabetes, infections, inflammation, cardiovascular issues, urinary tract issues, seizures and more, can be found here.

Dangerous Grapefruit Drug Interactions Known for 20 Years

Two decades ago, Bailey himself was among the first to discover that certain medications can interact dangerously with grapefruit when he and a team of researchers found that the combination can cause medication to concentrate in the patient’s blood. The drug simvastatin, for example, can concentrate by up to 330% when drinking three cups of grapefruit juice over the course of three days. Bailey said in certain patients and with certain medications, the concentration can be up to 1,000%.

According to Bailey, the interactions occur due to furanocoumarins, organic chemical compounds found in grapefruit, pomelos, limes, Seville oranges and certain other citrus fruits. Many citrus fruits, such as Valencia and navel oranges, do not contain furanocoumarins. These compounds interfere with CYP3A4, a digestive enzyme that assists in metabolizing toxins to prevent them from entering the bloodstream. Under normal conditions, this enzyme negates approximately half of any medication introduced to the body. As a result, consuming grapefruit along with certain medications can effectively result in a triple or quadruple dose.

Treating Warnings Seriously

As of now, medications known to interact with grapefruit are labeled as such, though Bailey feels that the warnings are overlooked or ignored all too frequently by the medical community and patients alike. He said that for every harmful interaction that’s reported, “at least 100″ more are never reported at all. Many people experience side effects when taking medication without even realizing that grapefruit is to blame, said Bailey.

Another problem, according to Bailey, is that the people who are most likely to need prescription medications — people over 45 years of age — are also the ones most likely to drink grapefruit juice. Worse still, people over the age of 70 have more trouble tolerating high dosages of drugs than younger people.

The takeaway for doctors and patients is to be more conscious of medication labeling, and to treat warnings about possible grapefruit interactions more seriously. If you enjoy grapefruit but you’re prescribed a drug known to interact with it, ask your doctor for an alternative medication. In most cases, an alternative with similar therapeutic effects will be available.

Grapefruit Drug Interactions – The Bottom Line

If you drink grapefruit juice, eat grapefruit or indulge in certain other citrus fruits, you should carefully check the labeling on any medications you take to rule out the possibility of a harmful drug interaction. These interactions can be serious or even deadly, especially in older patients.

The full text of Bailey’s study can be found online in the Canadian Medical Association Journal.

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