Noretynodrel, or norethynodrel, sold under the brand name Enovid among others, is a progestin medication which was previously used in birth control pills and in the treatment of gynecological disorders but is now no longer marketed.

[8] It was specifically approved at this time in combination with mestranol for the treatment of gynecological and menstrual disorders.

[8][14][15] Due to its nature as a relatively weak progestogen, noretynodrel is no longer used in medicine.

[10][16][18] No adverse effects have been observed in breastfeeding infants whose mothers were treated with noretynodrel.

[6] There is a reported case of signs of masculinization in a female infant whose mother was treated with noretynodrel for threatened miscarriage during pregnancy.

[3] It is considered to be a prodrug, and for this reason, the metabolites of noretynodrel play an important role in its biological activity.

[2] Noretynodrel is also thought to be a prodrug, as it is rapidly metabolized and cleared from circulation and shows very weak relative affinity for the progesterone receptor (PR), although it appears to form norethisterone in only minor quantities.

[8][3] Relative to norethisterone, noretynodrel has 45 to 81% lower affinity for the androgen receptor (AR).

[21] In accordance, no androgenic effects (such as hirsutism, clitoral enlargement, or voice changes) have been observed with noretynodrel even when used in large dosages (e.g., 60 mg/day) for prolonged periods of time (9–12 months) in the treatment of women with endometriosis.

[21] Noretynodrel, unlike most progestins but similarly to etynodiol diacetate, has some estrogenic activity.

[26] However, controversy on this matter exists, and other researchers have suggested that tibolone and noretynodrel may be aromatized in small amounts to highly potent estrogens (ethinylestradiol and its 7α-methyl derivative, respectively).

[3][2][4][29] Due to its very short elimination half-life and its low affinities for steroid hormone receptors in receptor binding assays, noretynodrel is considered to be a prodrug which is rapidly transformed into its active metabolites in the intestines and liver following oral administration.

[31][30] Noretynodrel was first synthesized by Frank B. Colton of G. D. Searle & Company in 1952, and this was preceded by the synthesis of norethisterone by Luis E. Miramontes and Carl Djerassi of Syntex in 1951.

[8] In 1957, both noretynodrel and norethisterone, in combination with mestranol, were approved in the United States for the treatment of menstrual disorders.

[6][16][18][31] Noretynodrel has been marketed by alone under the brand names Enidrel, Orgametril, and Previson and in combination with mestranol under the brand names Conovid, Conovid E, Enavid, Enavid E, Enovid, Enovid E, Norolen, and Singestol.