Prescription Drugs And Grapefruit Can Be Bad Medicine
November 27, 2012

Negative Affects Due To Interactions Of Some Prescription Drugs With Grapefruit

Connie K. Ho for — Your Universe Online

A new study published in the Canadian Medical Association Journal shows that, while there is a rise in the number of prescription drugs that result in negative effects due to interactions with grapefruit, few physicians are aware of these consequences.

The article was completed by a group of researchers who discovered the interactions among grapefruit and prescription drugs over 20 years ago. By summarizing the evidence available, they provide clinicians with more information as to what can happen when people consume certain foods with particular prescription drugs.

"Many of the drugs that interact with grapefruit are highly prescribed and are essential for the treatment of important or common medical conditions," remarked Dr. David Bailey, a researcher from Lawson Health Research Institute in London, Ontario, in the paper along with others coauthors. "Recently, however, a disturbing trend has been seen. Between 2008 and 2012, the number of medications with the potential to interact with grapefruit and cause serious adverse effects“¦has increased from 17 to 43, representing an average rate of increase exceeding 6 drugs per year. This increase is a result of the introduction of new chemical entities and formulations."

The negative effects that could occur include acute kidney failure, bone marrow suppression, gastrointestinal bleeding, renal toxicity, sudden death, among other significant side effects.

"One tablet with a glass of grapefruit juice can be like taking five or 10 tablets with a glass of water and people say I don't believe it, but I can show you that scientifically it is sound,” Bailey told BBC News. "So you can unintentionally go from a therapeutic level to a toxic level just by consuming grapefruit juice."

The researchers believe that there are over 85 drugs that have some kind of interaction with grapefruit, and 43 of those 85 result in negative side effects. Other citrus fruits like Seville oranges may also have active ingredients that are found within the fruit that lead to an unchangeable inhibition of the drug metabolizing CYP3A4 enzyme that usually inactivates the effects of approximately 50 percent of all medications. These drugs are normally given orally, completing drug metabolism in the gastrointestinal tract with the help of CYP3A4. They also have between low and intermediate bioavailability, which is a low percentage of the drug becoming absorbed into the blood circulation.

"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," noted the authors in the journal article. "In addition, the patient may not volunteer this information. Thus, we contend that there remains a lack of knowledge about this interaction in the general healthcare community."

According to The Telegraph, the article listed a number of prescription drugs affected by medications. These drugs included Tyverb (used for breast cancer), Amiodarone (helps stop blood clots following surgery), Clopidogrel (works in thinning blood), Dronedarone (focuses on heart rhythm disorder atrial fibrillation), Rivaroxaban (also focuses on thinning blood to stop strokes), Buspirone (targets anxiety), Fentanyl (manages pain relief), Domperidone (targets sickness), Atorvastatin (used by patients with high cholesterol), and Simvastaswtin (also utilized by patients with high cholesterol).

Furthermore, the team of investigators believed that the interaction can happen when an individual eats the grapefruit hours before ingesting the medication. Those who are older than 45 years will have the most exposure to the interactions, as they are the ones who tend to buy grapefruit and have prescriptions for those certain drugs. The Guardian reported that older aged adults have more difficulty in tolerating high systemic drug concentrations and become vulnerable to the interactions.

"The current trend of increasing numbers of newly marketed grapefruit-affected drugs possessing substantial adverse clinical effects necessitates an understanding of this interaction and the application of this knowledge for the safe and effective use of drugs in general practice," wrote the authors in the concluding section of the paper.

Medical professionals believed the results of the paper as significant.

"Although some of these interactions may not be clinically significant, some may lead to more serious outcomes,” stated Neal Patel of the United Kingdom´s Royal Pharmaceutical Society in the BBC article. "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."