Norethisterone

Norethisterone, also known as norethindrone, is a synthetic progestational hormone belonging to the 19-nortestosterone-derived class of progestins. It is further classified as a second-generation progestin, along with levonorgestrel and its derivatives, and is the active form of several other progestins including norethynodrel and lynestrenol. Norethisterone mimics the actions of endogenous progesterone, albeit with a greater potency, and is used on its own or in combination with estrogen derivatives in a variety of applications including contraception and hormone replacement therapy. First derived in 1951 in Mexico City, norethisterone was originally intended for use as a remedy for irregular menstruation and endometriosis, and was not marketed for use as an oral contraceptive until 1962.

Norethisterone is indicated as an oral contraceptive when given as monotherapy or in combination with an estrogen component, such as ethinylestradiol or estradiol. In combination with an estrogen component, oral norethisterone is also indicated as a hormone replacement therapy in the treatment of postmenopausal osteoporosis and moderate-to-severe vasomotor symptoms arising from menopause. When applied via transdermal patch, the combination of norethisterone and estradiol is indicated for the treatment of hypoestrogenism, vulvovaginal atrophy, and moderate-severe vasomotor symptoms.

Norethisterone, taken in combination with intramuscular leuprolide, is also indicated for the symptomatic treatment of endometriosis-related pain.