Sunday, December 2, 2012

Grapefruit, Medicine Interaction Warning Expanded


It has long been known that grapefruit juice can pose dangerous — and even deadly — risks when taken along with certain medications.

Dr David Bailey, a professor of pharmacology and one of the first to report the interactions between grapefruit juice and certain medications 20 years ago, warned that there had been a ‘marked increase’ in prescription drugs that interact with grapefruit.

‘This increase is a result of the introduction of new chemical entities and formulations.’

There are now more than 85 drugs that may interact with grapefruit, and 43 can have serious side effects. Such drugs, include statins, antibiotics, antidepressants, drugs to treat cancer and heart disease, plus others used by patients who have had organ transplants.


Grapefruits contain chemicals called furanocoumarins that cause the interaction by irreversible inhibition of the drug metabolizing CYP3A4 enzyme that normally breaks down drugs before they enter the bloodstream.

By preventing this normal breakdown of a drug, these chemicals in grapefruit can effectively cause a drug overdose and more severe side-effects.

“The frequency of these reactions may be small, but the risks are not worth it, especially for drugs which could cause sudden death,” said Dr Bailey.

Adverse effects include sudden death, acute kidney failure, respiratory failure, gastrointestinal bleeding, bone marrow suppression in immunocompromised people, renal toxicity and other serious side effects.

Other fruits including Seville oranges, limes, and pomelos can have the same effect, although sweet orange varieties do not produce this interaction.

The best advice for consumers, may be to ask a doctor or pharmacist when they are prescribed a new drug whether there are foods or other medicines that they should avoid.


The above story is based on the November 26, 2012 news release by the Canadian Medical Association.

The research has been published ahead of print in the Canadian Medical Association Journal:
Bailey DG, Dresser G, Arnold JMO. Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? CMAJ cmaj.120951; 

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