pharmacokinetics of estradiol pharmacokinetics of estradiol the pharmacology of estradiol, an estrogen medication and naturally occurring steroid hormone, concerns its pharmacodynamics, pharmacokinetics, and various routes of administration. pharmacokinetics of estradiolclinical dataroutes ofadministration• by mouth (tablet)• sublingual (tablet)• intranasal (nasal spray)• transdermal (patch, gel, cream, emulsion, spray)• vaginal (tablet, cream, suppository, insert, ring)• im injection (oil solution)• sc injection (aq. soln.)• subcutaneous implantdrug classestrogen; antigonadotropinpharmacokinetic databioavailabilityoral: 5% (0.1–12%)sl: 10% (in marmosets)im: 100%protein binding~98%:• albumin: 60%• shbg: 38%• free: 2%metabolismliver (via hydroxylation, sulfation, glucuronidation)metabolitesmajor (90%):• estrone• estrone sulfate• estrone glucuronide• estradiol glucuronideelimination half-lifeoral: 13–20 hourssublingual: 8–18 hourstransdermal (gel): 37 hoursim (as ev): 4–5 daysim (as ec): 8–10 daysiv (as e2): 0.5–2 hoursexcretionurine: 54%feces: 6% estradiol is a naturally occurring and bioidentical estrogen, or an agonist of the estrogen receptor, the biological target of estrogens like endogenous estradiol. due to its estrogenic activity, estradiol has antigonadotropic effects and can inhibit fertility and suppress sex hormone production in both women and men. estradiol differs from non-bioidentical estrogens like conjugated estrogens and ethinylestradiol in various ways, with implications for tolerability and safety. estradiol can be taken by mouth, held under the tongue, as a gel or patch that is applied to the skin, in through the vagina, by injection into muscle or fat, or through the use of an implant that is placed into fat, among other routes. routes of administration