Grapefruit and Your Rx Don't Mix

Grapefruit can interact with a number of medications

(RxWiki News) Grapefruit is a healthy fruit, but it can interact with some drugs. A review of research found that the number of drugs that might interact with grapefruit is on the rise.

The review found that there are now 85 different drugs that can interact with grapefruit.

The lead researcher reported the harmful effects from drug interactions happened when people consumed any amount of grapefruit. Older people may be at the highest risk of these types of adverse events.

"Tell your pharmacist if you eat grapefruit."

The review paper, with David G. Bailey, PhD, of the Lawson Health Research Institute as first author, reviewed the published studies about grapefruit and drug interactions. They found that 85 drugs have possible interactions with grapefruit. Many of them are commonly prescribed.

The number of drugs on the market that can cause serious or life threatening interactions with grapefruit is also on the rise. In 2008, there were 17 drugs listed that could cause serious health problems when taken with grapefruit.  In 2012, the number had risen to 43.

Grapefruit and possibly other citrus fruits can interact with an enzyme that is used to break down drugs.  When grapefruit is taken with some drugs, it gets in the way of this enzyme. If this happens, the drug stays active for longer. This interaction can result in overdose or prolonged exposure to the drug.

All forms of grapefruit - fresh, frozen, concentrate and juice – can interact with this enzyme.

Some of the studies reviewed showed that very large amounts of grapefruit were needed to cause an interaction effect – like a gallon a day of juice. But other studies showed problems when people ate typical amounts, like one grapefruit for breakfast each morning.

The review found that interactions occurred whether people were taking a new drug or one they had already been taking. Some interactions happened when people were stable on their drug then added grapefruit to their diet. Other interactions occurred when people started taking a drug while they were ingesting grapefruit regularly.

Most of the interactions happened when people were eating or drinking grapefruit on a regular basis.

Dr. Bailey cautions in the review that older people are at greater risk of interactions between grapefruit and medications. They take more meds and are the biggest consumers of grapefruit juice.

There are drugs to treat many conditions that can interact with grapefruit. The type of problem that is caused by the interaction depends on the drug type.

The list of drugs that can interact with grapefruit is long. Some drugs used to treat heart conditions and high cholesterol can interact with grapefruit, as can some anticancer, antibiotics, antipsychotics and antidepressants. This study was published November 26 in the Canadian Medical Association Journal. The authors declare no competing interests.

Review Date: 
November 27, 2012