Progestins in Combined Contraceptives

While the estrogen component of oral contraceptive pills is kept at 20–30 μg of ethinyl estradiol/day, attention in the development of new combined contraceptive drugs has been focused on the progestin component. Most of the antiovulatory effects of oral contraceptive pills derive from the action of the progestin component. The estrogen doses in these drugs are not sufficient to produce a consistent antiovulatory effect. The estrogenic component of combined contraceptives potentiates the action of the progestin and stabilizes the endometrium so that breakthrough bleeding is minimized. Besides the natural progestin, progesterone, there are different classes of progestins, such as retroprogesterone, progesterone derivatives, 17α-hydroxyprogesterone derivatives, 19-norprogesterone derivatives, 19-nortestosterone derivatives, and spironolactone derivatives. In addition to the progestrogenic effect, which is similar for all progestins, there is also a wide range of biological effects. The objective of this review article is to provide recent data on progestins currently available worldwide for contraception.