Interestingly, (from this study, Pharmacology of estrogens and progestogens: influence of different routes of administration, CLIMACTERIC 2005;8(Suppl 1):3–63), injectables are the only non-oral route that give a ratio estradiol:estrone similar to that in pre-menopausal females, 2:1.
-Post-menopause and intranasal estradiol give a 1:2 ratio.
-Sublingual gives an average of 3:1 BUT this is an average taking into account the very high ratio of estradiol to estrone in the first 2 hours. The same could actually be said of the intranasal route where levels spike at first.
-Subcutaneous implants (pellets) also yield a ratio close to the natural ratio, a 1.5:1 ratio.
-Patch and gel give a 1:1 ratio. While vaginal gives a 5:1 ratio!
Finally, oral gives a ratio of 1:5.
