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. It was available both alone and in combination with an estrogen. The medication is taken by mouth.

Noretynodrel is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone. It is a relatively weak progestogen. The medication has weak estrogenic activity, no or only very weak androgenic activity, and no other important hormonal activity. It is a prodrug of various active metabolites in the body, such as norethisterone among others.

Noretynodrel was introduced for medical use in 1957. It was specifically approved at this time in combination with mestranol for the treatment of gynecological and menstrual disorders. Subsequently, in 1960, this formulation was approved for use as a birth control pill. It was the first birth control pill to be introduced, and was followed by birth control pills containing norethisterone and other progestins shortly thereafter. Due to its nature as a relatively weak progestogen, noretynodrel is no longer used in medicine. As such, it is no longer marketed.

Noretynodrel was formerly used in combination with the estrogen mestranol in the treatment of gynecological and menstrual disorders and as a combined birth control pill. It has also been used in the treatment of endometriosis at high dosages of 40 to 100 mg/day. The medication has been discontinued, and is no longer marketed or used medically.

No adverse effects have been observed in breastfeeding infants whose mothers were treated with noretynodrel. Because of this, the American Academy of Pediatrics has considered noretynodrel to be usually compatible with breastfeeding.

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

Noretynodrel has weak progestogenic activity, weak estrogenic activity, and no or only very weak androgenic activity. It is considered to be a prodrug, and for this reason, the metabolites of noretynodrel play an important role in its biological activity. As such, the pharmacodynamics of noretynodrel cannot be understood without reference to its metabolism.

Noretynodrel is closely related to norethisterone and tibolone, which are the δ⁴-isomer and the 7α-methyl derivative of noretynodrel, respectively. It is metabolized in a very similar manner to tibolone, whereas the metabolism of norethisterone differs. Both noretynodrel and tibolone are transformed into 3α- and 3β-hydroxylated metabolites and a δ⁴-isomer metabolite (in the case of noretynodrel, this being norethisterone), whereas norethisterone is not 3α- or 3β-hydroxylated (and of course does not form a δ⁴-isomer metabolite). The major metabolites of noretynodrel are 3α-hydroxynoretynodrel and to a lesser extent 3β-hydroxynoretynodrel, formed respectively by 3α- and 3β-hydroxysteroid dehydrogenases (AKR1C1–4), while the δ⁴-isomer norethisterone is a minor metabolite formed in small amounts.