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The elimination half-life of levonorgestrel is 24 to 32 hours, although values as short as 8 hours and as great as 45 hours have been reported. [4] [6] About 20 to 67% of a single oral dose of levonorgestrel is eliminated in urine and 21 to 34% in feces. [6]
Whereas the biological half-life of estradiol given by intravenous injection is about 0.5 to 2 hours, the biological half-life of oral estradiol has a range of 13 to 20 hours due to the large and long-lasting pool of estrogen conjugates that is formed during first-pass metabolism and that serves to continuously replenish circulating estradiol ...
The pharmacokinetics of estradiol, including its bioavailability, metabolism, biological half-life, and other parameters, differ by route of administration. [11] Likewise, the potency of estradiol, and its local effects in certain tissues, most importantly the liver, differ by route of administration as well. [11]
Estradiol is an estrogen, or an agonist of the nuclear estrogen receptors (ERs), the estrogen receptor alpha (ERα) and the estrogen receptor beta (ERβ). [1] [2] [6] In one study, the EC 50 Tooltip half-maximal effective concentration value of estradiol for the human ERα was 50 pM (0.05 nM) and for the human ERβ was 200 pM (0.2 nM).
This results in a longer circulation half-life for the protein, and raised levels. ... 60 <0.1 <0.1 Flutamide: Nonsteroidal <0.01 <0.2 ... Levonorgestrel: 50 <1 ...
60 μg/day 500 L/day 0.7–2.8 nmol/L 20–81 ng/dL Estrone: Follicular phase 110 μg/day 80 μg/day 2200 L/day 110–400 pmol/L 30–110 pg/mL Luteal phase 260 μg/day 150 μg/day 2200 L/day 310–660 pmol/L 80–180 pg/mL Postmenopause 40 μg/day Insignificant 1610 L/day 22–230 pmol/L 6–60 pg/mL Estradiol Follicular phase 90 μg/day 80 ...
The ovulation-inhibiting dose of norgestrel appears to be greater than 75 μg/day, as ovulation occurred in 50 to 75% of cycles with this dosage of norgestrel in studies. [17] The ovulation-inhibiting dosage of levonorgestrel, which is twice as potent as norgestrel, is approximately 50 to 60 μg/day.
[1] [3] With a typical oral contraceptive dosage of norgestimate of 200 to 250 μg/day, an amount of 50 to 60 μg/day levonorgestrel may be produced. [22] This is similar to the ovulation-inhibiting dosage of levonorgestrel, and suggests that norgestimate may act in considerable part as a prodrug specifically of levonorgestrel.