From the library of

Frank Barnhill M.D.
 

The American Heart Association has long advocated we consume heart healthy fruits such as grapefruit, in our daily diet. The recommendation seems very good since grapefruit is low in calories, has essentially no fat content, is loaded with vitamin C and potassium and has a high fiber content.

Unfortunately, unlike other citrus foods such as oranges, grapefruit both as a juice and as the solid fruit can cause problems with a lot of common drugs used to treat heart disease, high blood pressure, high cholesterol, and cancer. One of the problems caused by grapefruit may include increased drug blood levels leading to an increase in serious side effects of the drug, including death. Another possible side effect of eating or drinking grapefruit when taking medications is a decrease in drug blood levels due to failure of the drug to be properly metabolized or converted to its active components. Of course, this results in not enough medication being present in your bloodstream to properly treat your illness.

A lot of medications you take are metabolized in your intestinal tract prior to entering your bloodstream, by a chemical process involving what is called the Cytochrome P450 3A4 system (CYP 3A4). This system uses enzymes and chemicals to change all or parts of the drugs you take in such a way as to make them available for use by your muscles, nerves, liver, brain, heart, blood vessels, and other body systems.

Unfortunately, grapefruit products have been shown to inhibit or keep your CYP 3A4 from working properly for up to 72 hours after they are eaten. No one knows exactly how this happens or what is present in grapefruit to cause it. The problem was accidentally discovered during a research project using grapefruit juice to hide the taste of ethanol alcohol. 

So what can possibly happen if you eat or drink grapefruit and take one of those drugs?

A change in normal drug blood drug levels can cause:

Flushing   swollen legs   headaches   rapid heart rates   skipping heart beats   liver damage

Lung damage  thyroid damage   heart attack   vomiting   abdominal pain   muscle damage  fatigue  low blood pressure   death

Key point: Everyone has different levels of CYP 3A4, so we are not all affected to the same extent by eating or drinking grapefruit.

Not every drug is affected by grapefruit juice and there are alternatives that can be used in most cases. Here are the most common medications that interact badly with grapefruit products:

Heart and blood pressure medications

Felodipine  nifedipine  nicardene  nisoldipine  nimodipine 

amiodarone  quinidine  disopyramide

Cholesterol and lipid lowering medications

Simvastatin  lovastatin  atorvastatin

Cancer therapy medications

cyclosporine

There are a number of other drugs thought to interact with grapefruit. such as estrogens, sildenafil, warfarin, angiotensin receptor blockers, buspirone and fexofenadine, but have not been conclusively or consistently proven to do so.

So, what should you do to avoid a grapefruit medication interaction?

• Discuss possible drug food ingestion problems with your doctor. This is especially true if  you have been having any of the side effects discussed above. (My editor pointed out that few people would report death as a side effect, so let’s avoid letting things get that bad!)
• Ask for alternative “grapefruit safe” drugs to treat your condition
• Avoid grapefruit products for 72 hours before taking and probably 8 hours after taking the above named medications
  Key point: A lot of people think that taking their pills three or four hours after eating grapefruit products will help avoid the drug interaction problems. Wrong!
  It clearly takes up to three days or 72 hours for the CYP 3A4 system to recover from the effects of grapefruit!
• Substitute other citrus fruits such as oranges, lemons, and pineapples in your diet

As you can see, taking medications to control and treat your illnesses and diseases sometimes involves making complex decisions and possibly even having to give up eating certain foods. Advances in medicine, such as this one, are what have helped us live longer and healthier lives.

Here’s to healthier living!

Dr. Frank