More about the grapefruit effect on Viagra....
Life Sci 1998;62(10):PL135-PL142
Mechanism-based inactivation of human cytochrome P450 3A4 by grapefruit juice and red wine.
Chan WK, Nguyen LT, Miller VP, Harris RZ
Department of Pharmaceutics and Medicinal Chemistry, School of Pharmacy, University of the Pacific, Stockton, CA 95211, USA. wchan2@uop.edu
Grapefruit juice is well documented to cause clinically significant increases in the plasma concentrations of many therapeutic agents. These interactions are believed to be mediated via inhibition of intestinal cytochrome P-450 3A4 (CYP3A4) by flavonoids and/or other chemicals in grapefruit juice, although the mechanism of that inhibition has not been fully characterized. Like grapefruit juice, red wine contains large amounts of flavonoids and other xenobiotics which could also mediate CYP3A4 inhibition. In this study, we investigated the mechanism of inhibition of CYP3A4 by grapefruit juice and also examined the ability of red wine to inhibit this enzyme. Both red wine and grapefruit juice potently inhibited CYP3A4 activity in a concentration-dependent manner. At 8% of natural strength, enzyme activity was inhibited almost 90 and 84%, respectively, by grapefruit juice and red wine. In contrast, white wine did not appreciably inhibit CYP3A4 activity. Grapefruit juice irreversibly inactivated CYP3A4 in a time- and NADPH-dependent manner. The rate of inactivation mediated by grapefruit juice was similar to that mediated by troleandomycin, a potent mechanism-based inhibitor of CYP3A4. Red wine also inactivated CYP3A4 but at a rate approximately 16% that of grapefruit juice. Inhibition of CYP3A4 by red wine is primarily reversible in nature. The clinical implications of this research are discussed.
I guess Viagra is like fish, only goes with white wine.
Seriously, some of those sexy seniors are also drinking lots of fruit juices and taking bioflavinoid supplements for their atherosclerotic prevention. This study suggests that the Cyt P450 (CYP3A4) is inhibited 90% by grapefruit juice with only 8% real grapefruit juice (common in commercial fruit drinks to be only about 10% real juice.) A friend of mine is a cardiologist who is very big on flavenoids, I always know when he has referred a patient to me, because they are all taking the bioflavinoids (look in your supermarket vitamin section, flavinoid supplements are available without a prescription) And now of course, we have the atherosclerotic patient as a prime target market for Viagra.
Zebra
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