Grapefruit Juice and Medications

November 10, 2005

Grapefruit Juice and Medications (Viagra Catches your Attention!) 

 Competency #14  SUPERFOODS                     Reference:  Web MD and Grapefruit Juice 

 It's getting to be grapefruit season.  I just ordered a case in a fundraiser at church.  20% of Americans drink grapefruit juice regularly.  You may have heard that it affects medications, but never knew how or why. First of all, grapefruit is a nutritional star.  It has tons of Vit C and potassium.  And remember, increasing your intake of potassium from food sources is strongly correlated with lowering your blood pressure.  So as a food, grapefruit scores high with many organizations like the American Heart Association. 

 There has been some study on just which of the hundreds of trace elements in grapefruit juice get you in trouble.  The leading candidate is something called "furanocoumarin".   What it does is tricky.  It BLOCKS an enzyme (CYP3A4) in your intestine that slows or reduces the absorption of some drugs.  This will allow the drug to get into your system faster and for a long period of time.  It only takes a single glass of grapefruit juice to boost drug absorption as much as 45% and still have a 33% effect 24 hours later.  That's pretty potent stuff. 

 Here are the drug families that are affected.  Calcium channel blockers, statins, benzodiazepines, and some neurological drugs like BuSpar, Zoloft and Tegretol.  If you are on any of those drugs, you can Google on Web MD and ask the question what to do with grapefruit juice and your drug.  You may want more statin effect as it may be a way to boost the effectiveness of your statin.  But then, you should take grapefruit juice regularly and have your lipid response checked.  Considering that there have been recent suggestions that more aggressive statin use is in order, you may get the effect without having to pay for a higher dose.  Talk to your doctor about this. 

 As a final note, Viagra is substantially boosted by drinking grapefruit juice which blocks the CYP3A4 enzyme in the gut.  Drinking grapefruit juice with Viagra may compound the effects of Viagra: both good and bad.  It may slow a man's heart rate and drop his blood pressure more than expected.   And as they say on the TV adds for a competitor of Viagra, "If it lasts more than four hours, seek medical attention". 

 WWW: What Will Work for Me.  I love grapefruits.  They take work to fix which is a problem when I’m in a hurry.  If I can get over that threshold of cutting them up, they are part of that midwinter delicious fruit that we should all embrace.  It’s such a loving thing to have a grapefruit prepared for you.  Think of returning the favor… to yourself and your loved ones living with you. 

This column was written by Dr. John E. Whitcomb, Brookfield Longevity, Brookfield, WI. (262-784-5300)