Ask the Doctors

Dear Doctor: Years ago, I was told not to consume grapefruit or grapefruit juice with statins. Now I understand that this restriction no longer applies. Is this correct?

Dear Reader: The reason people are warned to steer clear of grapefruit when taking statins, which are drugs that lower cholesterol, is that certain compounds within the fruit and its juice affect the way the medications are absorbed. Known as furanocoumarins, they interfere with the metabolic processes that break down a range of medications, including statins. And while you're correct that there are now a few brands of statins that don't interact with those compounds, it's important to check with your pharmacist or physician regarding your particular prescription before adding grapefruit to your diet.

Statins are a class of drugs that get broken down with the help of an enzyme known as CYP3A4, which is found in the gastrointestinal tract and liver. It's a process that controls how much of a drug is released into the bloodstream, and it is factored into the calculations used to determine drug dosages. What happens in the presence of furanocoumarins, which are found not only in grapefruit but also in pomelos and Seville oranges, is the work of that key enzyme is inhibited. As a result, a larger amount of the drug than is intended enters the blood and accumulates in the body. In the case of statins, too much of the drug in the body can lead to grave complications, such as increased risk of damage to the liver and muscles, which can lead to kidney failure.

Grapefruit is a good source of vitamin C and has a bit of potassium as well, so patients often ask if there's a minimum amount they can safely consume while taking statins. Unfortunately, with many statins, the answer is still no. That's because we each secrete a different amount of the CYP3A4 enzyme in the small intestine. The same glass of grapefruit juice that would be safe for one person would be dangerous for someone else.

Interestingly, that same compound that generates an overabundance of statins in the blood will decrease the available amount of a few other drugs, including fexofenadine, an allergy medicine sold under the brand name Allegra. Apple juice and orange juice have the same effect on fexofenadine, which is why the labels on both the prescription-level and over-the-counter varieties of the drug carry a warning against taking it with any fruit juices.

An estimated 20 percent of the population between the ages of 45 and 70 are prescribed statins, so the fact that several of the brands now available do not appear to affect the CYP3A4 enzyme is good news. The statins that remain on the no-grapefruit list are atorvastatin (Lipitor), lovastatin (Mevacor) and simvastatin (Zocor). And while the current literature suggests that rosuvastatin (Crestor) and pravastatin (Pravachol) as well as a few other statin drugs have limited or no interaction with furanocoumarins, we urge you to check with your pharmacist or physician before adding grapefruit to your diet.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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