The number of drugs that interact with grapefruit has increased considerably in the last four years. Scientists warn that more information needs to be given on the risks to prevent dangerous side effects.
Grapefruit interacts with many different drugs
Writing in the Canadian Medical Association Journal, researchers revealed that the number of drugs causing serious side effects with grapefruit has increased from 17 in 2008 to 43 in 2012.
Chemicals in grapefruit called furnocoumarins prevent an enzyme in the body from breaking certain drugs down in the intestines and the liver. This means that more of the drug escapes the digestive system than the body can handle.
Side effects of the interaction vary depending on the drug, but can include stomach bleeds, altered heartbeat, kidney damage and sudden death.
The scientists at the Lawson Health Research Institute in Canada say that affected drugs are prescribed for a range of conditions, including anxiety, depression, blood pressure, cancer, HIV infection and high cholesterol.
A modest single helping of grapefruit can cause an interaction, even if consumed hours before a drug is taken. In the report, three times the level of one blood pressure drug was reported after patients had a glass of grapefruit juice compared with a glass of water. The report said:
"We contend that there remains a lack of knowledge about this interaction in the general health care community."
"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."
Other citrus fruits such as Seville organs and limes have the same effect. Neal Patel, from the Royal Pharmaceutical Society said: "Grapefruit isn't the only food that can cause issues, for example milk can stop the absorption of some antibiotics if taken at the same time.
"Although some of these interactions may not be clinically significant, some may lead to more serious outcomes.
"Pharmacists are the best port of call for anyone concerned about how their diet may affect their medication. Information about any interactions would always be included in the patient information leaflet that comes with the medicine."
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