synthetic progesterone used in oral contraceptives and as an emergency contraceptive. (Other Progestins: 3-keto-desogestrel, dienogest, drospirenone, Nestorone, nomegestrol acetate and trimegestone) Note that Trimegestone and Nestorone are currently the most potent fourth-generation progestins with no androgenic or estrogenic actions. (More? Human Menstrual Cycle)

a synthetic progestin used in several contraceptive products.

progestin. Named levonorgestrel because it is the levorotatory form of norgestrel. Used in combination with an estrogen as an oral contraceptive. Used alone for emergency contraceptive (in Plan B) and the treatment of menstrual disorders or endometriosis.