03-04-2014, 01:05
Thanks Lotus.
(03-04-2014, 01:05)peggy Wrote: Thanks Lotus.
Quote:Grapefruit juice inhibits drug metabolism at the GI tract, so its effects on estrogen would be most pronounced with oral dosage forms, leading to increased levels of estrogens in the bloodstream. We are recommending that women stay away from oral estrogens in most cases so that would help diminish any potential interactions, however, estrogens are enterohepatically recirculated (the estrogens circulate through the bile duct, through the GI tract and back into the circulation) so even with topical administration, there may be some effect. Of course, I recommend that women have their estrogen levels tested whenever they are on supplementation, and if a patient is having an interaction with grapefruit juice, it would be picked up as higher levels.
So, should women who are on transdermal estrogens avoid grapefruit juice? I guess it’s probably a good idea, but not an absolute.
Quote:Estrogen and progestin combination: Grapefruit may increase the bioavailability and side effects associated with estrogen (153; 154; 155). In one randomized crossover trial, grapefruit juice increased the ethinylestradiol Cmax significantly to 137% (p=0.0088) and increased the AUC(0-8) to 128% (p=0.0186) (155). Grapefruit juice has demonstrated the ability to alter the metabolic degradation of estrogens and increase the bioavailable amounts of 17beta-estradiol and its metabolite estrone in ovariectomized women (154). The most likely mechanism of action of the flavonoids of grapefruit juice on 17 beta-estradiol metabolism is the inhibition of the CYP450 3A4 enzyme, which catalyzes the reversible hydroxylation of 17 beta-estradiol into estrone and further into estriol (154).