Gel is likely better for e2/e1 ratio i think
With administration of an oral estradiol tablet sublingually, complete dissolution of the tablet occurs within a few minutes and circulating levels of estradiol begin to rise within 5 minutes.
[81] Maximal levels of estradiol occur after 30 to 60 minutes of administration.
[81] After this, estradiol levels drop steeply within 4 hours, and this is followed by a more gradual decline in levels of estradiol and a return to baseline concentrations by 24 hours.
[81] The rapid rise and steep fall of estradiol levels with sublingual administration of estradiol is analogous to the case of
intravenous injection and
intranasal administration of the hormone.
[9][11][4]
Sublingual administration of a single 0.25 mg tablet of micronized estradiol has been found to produce peak levels of 300 pg/mL estradiol and 60 pg/mL estrone within 1 hour.
[9] A higher dose of 1 mg estradiol was found to result in maximum levels of 450 pg/mL estradiol and 165 pg/mL estrone, which was followed by a rapid decline in estradiol levels to 85 pg/mL within 3 hours.
[9] Conversely, the decline in estrone levels was much slower and reached a level of 80 pg/mL after 18 hours.
[9] A single administration of 4 mg micronized estradiol (two 2-mg Estrace tablets) under the tongue, considered a very high dose of sublingual estradiol, has been found to result in maximal levels of estradiol of 1759 ± 704 pg/mL, with a range of 634 to 2840 pg/mL, after 1 hour in a mixed group of
normotensive and
hypertensive postmenopausal women.
[84]
Although sublingual administration of estradiol has a relatively short duration, the medication can be administered multiple times per day in divided doses to compensate for this.
[9][87][88] Studies that used high doses of sublingual estradiol in the treatment of severe
postpartum depression have administered a dose of 1 mg 3 to 8 times per day.
[89][90][87][88]
Regardless of administration form, such as patch or gel, transdermal estradiol is transported into the skin, including through the
stratum corneum,
epidermis, and
dermis, by a
passive diffusion process.
[9][117] Following this, estradiol is then taken up by local
capillary blood vessels and delivered into the circulation.
[9] There is a
depot effect in the skin with transdermal estradiol, which results in continuous delivery of transdermal estradiol into the circulation.
[17][117] This is because the skin functions as a
semipermeable membrane and there is a
concentration gradient between the application site of transdermal estradiol and capillary blood, with the rate of diffusion of estradiol across the stratum corneum being the specific
rate-limiting factor in absorption.
[9][117] As a result, peaks and troughs in circulating estradiol levels are limited, and the skin and
subcutaneous fat act as a reservoir of estradiol that maintains circulating estradiol levels between doses.
[17] For these reasons, transdermal estradiol can provide near-constant circulating levels of estradiol
unlike oral estradiol, transdermal estradiol is not associated with supraphysiological concentrations of estrone or estrogen conjugates like estradiol sulfate, and transdermal estradiol does not have disproportionate effects on liver protein synthesis.
[9] In accordance, estradiol, at typical menopausal replacement dosages, has been found not to increase the risk of blood clots or insulin resistance,
[55][11] nor to affect hepatic SHBG, IGF-1, GHBP,
[58] IGFBP,
[59]