Viagra and Grapefruit Juice?

I see conflicting information on this combination. anyone have any experience with it?

Grapefruit juice contains a CYP3A4 enzyme that is supposed to block the breakdown of certain drugs in the bloodstream. They warn people not to take the 2 together becasue it increases the blood levels of certain drugs (Viagra being on of them) Not only do you have increased blood levels but it also is supposed to lengthen the time it takes the body to break the drug down. They do say it slows absorbtion and also, part of having higher levels in the blood would also amplify the unwanted side effects.

The standard warnings advise against combining the two but I see other people saying they take it with grapefruit juice on purpose. What’s the deal here?

this is news to me!! The only advice I give about meals and viagra is to avoid fatty meals for 2 or 3 hours before taking it since the fat delays absorption. Could you give a regerence for the grapefruit thing. Conventional concepts of digestive physiology would suggest that an enzyme taken orrally would either be denatured and rendered inactive by stomache acid or digested by pepsin (the stomackes enzyme that breaks up protien - all enzymes are at least in part protien). However It may be that a small fracton gets into the systmic circulation somehow -

this would be contrary to conventional concepts however PE in general contrary to conventional concepts so I’ll keep an open mind.

hang10;

The theory does work in practice with Viagra and with certain other drugs including many blood pressure medications. For this reason those who rely on these drugs for their regulatory effects shouldn’t combine them with grapefruit juice.

As for Viagra, the fact is that in order to enhance its half-life you have to drink a pint of g. juice _every hour_. This results for many in a stomach churning with acid. Add to that the gastric side effects that Viagra itself often produces, you may just feel very nasty.

If you want to increase the speed of V working and get the highest peak plasma level of the drug, dissolve your dose in a couple ounces of water and get ready to roll.

this one gives you the warning:

from:
http://www.ti.u … es/letter32.htm

"Precautions: There is no safety information on patients excluded from the trials (e.g. patients with alcoholism, active peptic ulcer, proliferative diabetic retinopathy, etc.). Inhibitors of CYP3A4 such as erythromycin, ketoconazole, grapefruit juice and others would be expected to increase the magnitude and duration of response to sildenafil."

The component is a natural enzyme inhibitor not an enzyme that does make more sense. It would seem impractical to take that much grapefruit juice just to prolong the effect - it could turn out just as cheap to take another dose.