Estradiol vaginal administration

Estrogens are also subject to extensive first-pass effects (it has been shown that these first-pass effects occur predominantly in the intestinal wall, rather than in the liver) after oral administration. Again, vaginal administration of estradiol results in higher bioavailability than via the oral route (Figure 11 4(b)). 

Figure 11.4 Plasma levels of progesterone and estradiol in women after vaginal (yellow) or oral (blue) administration of progesterone 100 mg, or estradiol 0.5 mg. For full experimental details see Nahoul, K. et al, Maturitas, 16 185-202.

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