Grapefruit at centre of deadly cocktail

By Adela Talbot
December 06, 2012

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That glass of grapefruit juice you usually have with breakfast isn’t as healthy as you think – if you’re taking certain medications, that is. Perhaps you already knew that.

“We discovered the interaction 20 years ago. The science of grapefruit-drug interaction has been extensively studied. The science of the (interaction) is well known, but I don’t think it has been applied the way it needs to be now,” said David Bailey, professor emeritus in the Schulich School of Medicine & Dentistry’s Division of Clinical Pharmacology.

Bailey, along with colleagues George Dresser and J. Malcolm Arnold, recently published Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? The paper extensively outlines a rapidly growing list of medications that, when taken by individuals who consume grapefruit, could cause serious adverse effects, the most serious among them being sudden death from cardiac arrest.

“It is an educational document and it’s based on our concerns about the number of new drugs coming on the market with a potential to interact with grapefruit juice that results in very serious toxicities,” Bailey said. The number of drugs that could cause adverse effects is rapidly growing, while the caution that should accompany the prescriptions isn’t exactly in tow.

“From 2008-12 – that’s four years – the number of drugs with the potential for serious adverse effects (when consumed by people who drank grapefruit juice) has gone from 17 to 44. That’s an average of more than six new drugs per year coming on the market. This is the reason we felt we had to write it.”

The word is getting out. In the last week, the study has found its way out of the medical journal and into the mainstream press around the globe.

Bailey explained it is necessary for both patients and health professionals to understand grapefruit-drug interactions and for doctors and pharmacists to apply this information to the safe and effective use of medications in their practice. 

“We were really afraid (the new drugs on the market) would slip through the cracks because the information is not really easily accessible,” Bailey noted. He explained grapefruit-drug interaction is generally included in the medication’s monograph, but isn’t exactly accessible to the average patient.

Bailey and his team put together an accessible, eight-page document outlining medications that should not be taken with grapefruit, the list, likelihood and severity of an adverse reaction as well as potential alternate medications that would not cause serious side effects.

The most serious adverse effect is sudden death from cardiac arrest, Bailey said, noting among 27 drugs put on market in the last three years, 13 have the potential to produce sudden cardiac arrest death.

Other adverse effects include acute kidney failure, gastrointestinal bleeding, which can cause major hemorrhaging and be life threatening, respiratory failure and suppression of bone marrow function.

“This is not getting a headache – this is causing severe adverse reactions,” Bailey said.

He added it’s best not to have any grapefruit – no fruit or juice – as it takes less than a glass to negatively interact with medication. And it doesn’t matter when you take the medication or drink the juice – the effect of grapefruit is so long that it irreversibly inactivates an enzyme in the gastrointestinal tract that is responsible for metabolizing drugs.

“I think everybody needs to know about this so we don’t have to worry or experience a serious adverse effect. The bottom line is – the potential for adverse effects is known. It’s predictable and therefore, it’s preventable,” Bailey said.























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