Richard G. Petty, MD

Grapefruits, Medicines and Medical Correspondents

Mark Twain once said:
“Be careful of reading health books, you might die of a misprint.”

I was thinking about that as I was watching a TV show earlier.

I have spoken before about the frustration of many of us about the quality and accuracy of some media medical correspondents. Though every show has a disclaimer about the importance of discussing any issue with a health care provider, it is really unfortunate to present inaccurate data that could needlessly alarm people.

I will immediately put my hand up and say that I have done more than my share of media work, not just in the United States and Great Britain, but also in countries from Finland to Australia and twenty or thirty more in between. And I may well have misspoken at some time or other. Even the most well intentioned people sometimes make slips, and it is especially easy when you are in a studio and you know that the clock is counting down.

But that stress makes it all the more important to have accurate material prepared in advance so that slip-ups don’t happen.

Today’s piece was about a story that pink grapefruit may not interact with some medications. The correspondent rightly said that any type of grapefruit may interact with some medications, but then said that there was an interaction in the stomach. This is not correct and could be very confusing.

The issue is that grapefruit juice may induce the enzyme complex cytochrome P450 3A4 in the liver and intestine. So if you or a medication that is metabolized by the enzyme, grapefruit juice may lower the plasma level of the drug, making it less effective. This is another example of the importance of telling your health care provider about ANYTHING that you eat or drink, in addition to listing any herbs and supplements that you take.

Here is a list of some of the more common medicines metabolized by cytochrome P450 CYP3A4:

Alprazolam
Amiodarone
Amlodipine
Aripiprazole
Astemizole
Atorvastatin
Buspirone
Cafergot
Chlorpheniramine
Cimetidine
Cisapride
Clarithromycin
Cocaine
Codeine
Cyclosporine
Dapsone
Dexamethasone
Dextromethorphan
Diazepam
Diltiazem
Domperidone
Erythromycin
Estradiol
Felodipine
Fentanyl
Finasteride
Fluconazole
Fluvoxamine
Grapefruit juice
Faloperidol
Hydrocortisone
Iindinavir
Itraconazole
Ketoconazole
Lidocaine
Lovastatin
Methadone
Midazolam
Mifepristone
Nefazodone
Nifedipine
Nitrendipine
Norfluoxetine
Ondansetron
Pimozide
Progesterone
Propranolol
Quetiapine
Quinidine
Quinine
Risperidone
Ritonavir
Sildenafil
Simvastatin
Tacrolimus
Tamoxifen
Taxol
Telithromycin
Terfenadine
Testosterone
Trazodone
Triazolam
Verapamil
Vincristine
Ziprasidone
Zolpidem

About Richard G. Petty, MD
Dr. Richard G. Petty, MD is a world-renowned authority on the brain, and his revolutionary work on human energy systems has been acclaimed around the globe. He is also an accredited specialist in internal and metabolic medicine, endocrinology, psychiatry, acupuncture and homeopathy. He has been an innovator and leader of the human potential movement for over thirty years and is also an active researcher, teacher, writer, professional speaker and broadcaster. He is the author of five books, including the groundbreaking and best selling CD series Healing, Meaning and Purpose. He has taught in over 45 countries and 48 states in the last ten years, but spends as much time as possible on his horse farm in Georgia.

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