This would also seem to imply that drinking a lot of grapefruit juice would also put anyone not on warfarin at risk of major bleed type events.
No, it doesn't. I did a bit of research on this some time back for my own info. What the grapefruit juice does is reduce the body's ability to metabolize the warfarin that you are taking. So, the concentration of warfarin in your blood builds up to much higher levels than it would if your body were constantly clearing out the warfarin. So, if you _ARE_ taking warfarin, the effect is similar to taking more of it. If you are _NOT_ taking warfarin, no problem.
FYI: It appears to be more of an urban legend about cranberry juice affecting INR.
Again, I have done a lot of googling about this, and the jury appears to still be out. There are several studies that show no effect on groups of 250 or so folks drinking cranberry juice compared to placebo. There are, however, a few reported cases of individuals with apparent extreme INR sensitivity to cranberry juice. Because of recent identification of genetic markers indicating predisposition to over/under sensitivity/resistance to warfarin (google "warfarin pharmacogenetics" for lots of info) it may simply be that a few folks _MAY_ have some genetic variant that causes some sensitivity to cranberry juice similar to that of grapefruit juice.
Anecdotally, I recently had my own INR jump between 2.7 and 4.6 in 3 days, then back to 2.6 three days later, then back up to 4.5 four days after that, and the only change in my diet was some cranberry juice, about an 8 oz glass per day for the few days preceding the high readings. Although my INR is fairly bouncy to begin with, I do plan to run a somewhat more controlled experiment on myself to see if there is indeed any repeatable relationship that could be attributable to cranberry juice. I do have a home meter and can test frequently to ensure I stay within a reasonably safe range if it does start to climb. I don't recommend others try this, but if I find anything significant, I'll post something back to the forum.
if I'm consistent with my grapefruit juice, can I reduce the amount of warfarin I take?
I have been wondering the same thing, especially since I take a fairly large amount of warfarin for my maintenance dose. If I could substitute grapefruit or cranberry juice for some of the warfarin, I would feel like that would be a bit healthier. Unfortunately, my personal opinion is that even if it did work to some extent, this would be a much more unstable solution to hitting a target INR range, and your INR would be much more variable. The exact percentage of the "active ingredients" in the juice per fluid ounce are not guaranteed to be as consistent as pharmaceutical grade pills like warfarin. Plus, I suspect counting on the buildup of warfarin in the blood as a result of the slowing of the drug metabolization will be more dependent on other factors like daily physical activity - at least more so than taking warfarin alone to achieve the INR. Again, this is just my unsubstantiated personal opinion, although it might be interesting if some brave soul wants to give it a try. I'm _NOT_ going to try it myself, nor would I recommend it without extremely frequent monitoring of your INR.
