Estradiol valerate
In addition to single-drug formulations, oral estradiol valerate is available in combination with the progestin dienogest as a combined oral contraceptive and intramuscular estradiol valerate is marketed in combination with the progestins hydroxyprogesterone caproate and norethisterone enantate as combined injectable contraceptives. Intramuscular estradiol valerate has also been marketed in combination with testosterone enantate, but this formulation has been discontinued. The availability of estradiol valerate-containing products varies throughout the world.
Birth control pill formulations
All contain an estrogen, ethinylestradiol or mestranol, in varying amounts, and one of a number of different progestogens. (Regarding the estrogen, the inactive 3-methyl ether of ethinylestradiol, which must be metabolized by the liver into the active ethinylestradiol; 50 µg of mestranol is equivalent to only 35 µg of ethinylestradiol and should not be used when high-dose [50 µg ethinylestradiol] estrogen pills are needed; mestranol was the estrogen used in the first oral contraceptive, Enovid). They are usually taken for 21 days with then a seven-day gap during which a withdrawal bleed (often, but incorrectly, referred to as a menstrual period) occurs. These differ in the amount of estrogen given, and whether they are monophasic (the same dose of estrogen and progestogen during each of the 21 days) or multiphasic (varying doses). The introduction of extended-cycle monophasic pills (i.e. Seasonale) has shown that the withdrawal bleeding intervals can be decreased.