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Tue 9 May, 2006 11:45 am
Study finds how grapefruit juice affects drugs
WASHINGTON (Reuters) - U.S. researchers said they have identified the compound in grapefruit juice that affects how some drugs are absorbed in the body and said on Tuesday it might be used to help lower dosages for some patients.
Grapefruit juice is known for its effects on drug metabolism and is avoided by some patients while other deliberately take their drugs with the juice.
The reason is an intestinal enzyme called CYP3A, which partially destroys drugs as they are absorbed. Grapefruit juice, like no other fruit juice, interferes with CYP3A, so the body ends up absorbing more of the drug.
Dr. Paul Watkins of the University of North Carolina at Chapel Hill and colleagues say they have identified the substance in grapefruit juice that is responsible -- furanocoumarin.
"It should now be possible to market the furanocoumarin-free grapefruit juice to patients who would otherwise need to avoid grapefruit," Watkins said in a statement.
"In addition, it should be possible to screen new foods for the potential for drug interactions by determining whether they contain furanocoumarins," Watkins said.
"Finally, it may be possible to add furanocoumarins to formulations of certain drugs that tend to be poorly or erratically absorbed to improve their oral delivery."
To test the theory that furanocoumarin was the responsible compound, Watkins and colleagues filtered it out grapefruit juice, which they discovered was then less bitter but otherwise unaltered.
Then they tested 18 men and women taking various drugs on a regular basis including aspirin and birth control pills.
Each fasted in the hospital and got a single dose of the blood pressure drug felopidine, sold under the brand name Plendil, along with either normal grapefruit juice, furanocoumarin-free juice or orange juice.
They then ate and drank normally and blood was taken regularly all day.
In each volunteer, the normal grapefruit juice made between 6 percent to 230 percent more Plendil available in the blood, the researchers reported in the American Journal of Clinical Nutrition. The furanocoumarin-free grapefruit juice and orange juice had no such effect, they reported.
Cool, I love grapefruit juice and cannot drink it, at least not in any quantity.
At the same time, it might be a way to reduce my prescription drug costs. Cut my pills and just take a quarter of one with grapefruit juice. Hmm, never thought of that before.
I was taking a beta blocker and an ACE inhibitor for BP before I knew about grapefrui t juice. I took my pills and then downed a midsized glass of pink grapefruit juice freshly squozen. In about 3/4 hour I got up from the office chair I was sitting in and promptly passed out . I had MT'd an entire does which was time release.
The bad side, besides the passing out thing, you metabolize your drug all at once so theres no titer left which is what most phrma meds workings are predicated on. So any drug which has a built in stress buffer for needed times where need exceeds availability, just isnt there. --You die.
ACE inhibitors and Grapefruit juice
I have been taking Valsartan, Atenolol and Symvastatin on a regular basis. During a very hot two days 2 weeks ago (that's usually the extent of our normal "summer season" in Manchester (UK), I consumed 1'5 litres of pure grapefruit juice.
2 days later I passed out and was rushed into hospital because my BP had dropped to a ridiculously low level and my heart was beating at around 50 beats a minute. Since (at 66) I don't consider myself to be an extremely fit Olympic athlete (well - maybe in my head!) I knew something was really wrong.
The A & E Dept almost insisted I had had a heart attack despite my telling them I had no pain and was not dyspnoeic (short of breath)
About 1 hour after being admitted I began to pass copious amounts of urine which is most unusual for me and I felt extremely light headed from the severe drop in BP ( 90/55 ) I mentioned this to the medical staff but my observations were not noted.
My first lot of blood samples showed no evidence of cardiac involvement, nor was there any abnormality in my blood glucose level.
However there was a significant increase in creatinine and urea in my blood which was commented on but no connection was made to my prevailing signs and symptoms.
The following day I was discharged without any explanation as to why this experience had occurred, but my BP and pulse were well below my norm.
It was only after a casual (unrelated) conversation that I remembered drinking the grapefruit juice during the 2 days prior to my collapse and that triggered off a "response" in my ever failing memory.
When I checked this out on the internet I was amazed to find so many articles related to taking the very drugs prescribed for me and grapefruit juice.
Neither my own GP, nor the hospital doctors, seem to be aware of this interaction - which amazes me, because if I can find the information, surely ALL doctors should be aware of this interaction.
Maybe it's time that the BMA or GMC in the UK received a general mail shot about this subject, considering the millions of people taking these particular drugs and unknowingly putting themselves at risk of a potentially life threatening situation.
Maybe it's up to patients to INSIST that their doctors read the abundance of available evidence.
There again, the obvious action for any patient at risk is not to stop taking these very important drugs - JUST STOP DRINKING OR EATING GRAPEFRUIT!
I hope my message saves others from the quite frightening experience I suffered.
Wow, Harold Myers, thanks for posting that, and welcome to A2k. You happened to post here at a time when the site is going through a maintenance period and has been quite sluggish, temporarily.
The trouble with depending on grapefruit to make your drugs more bioavailable, and therefore able to take lower doses, is that grapefruit varies greatly in its effect, even in individuals. You can't guarantee what's in your grapefruit and expect the same effect each time.
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