Norethindrone

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Cat Number

API0231599

CAS Number

68-22-4

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Product Detail Description Scientific Support Customer Q&A

CAS Number

68-22-4

EINECS

200-681-6

Storage

Store at room temperature

Synonyms

Micronor; Norethisteron; Norlutin; 19-Norethisterone; Anovule; Gestest; Micronovum

Molecular Formula

C20H26O2

Molecular Weight

298.4

Smiles

C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@]2(C#C)O)CCC4=CC(=O)CC[C@H]34

Appearance

White to creamy white crystalline powder

Melting Point

205-206℃

Boiling Point

447℃ (Predicted)

General Description

Norethindrone (also known as norethisterone) is a synthetic progestin belonging to the 19-nortestosterone class, widely used in oral contraceptives and hormone replacement therapy. It is available as single-ingredient tablets (e.g., for endometriosis) and in combination with estrogens. The drug exhibits partial androgenic activity, distinguishing it from other progestins.

Mechanism of Action

Norethindrone binds to progesterone receptors in target tissues, inducing secretory changes in the endometrium and stabilizing the endometrial lining. It also suppresses gonadotropin (LH and FSH) release via negative feedback on the hypothalamic-pituitary axis, preventing ovulation. The drug's weak androgenic properties derive from its ability to interact with androgen receptors, which can cause side effects like acne and weight gain but also contribute to endometrial protection.

Application

Norethindrone is indicated for the treatment of abnormal uterine bleeding, endometriosis (as monotherapy or with estrogen), amenorrhea, and as the progestin component in combined oral contraceptives.

In a pilot randomized controlled study (50 women), norethindrone 5 mg three times daily, started on or before cycle day 12, was compared with combined oral contraceptives (OCPs) for delaying menstruation. Only 8% of norethindrone users reported spotting versus 43% of OCP users (p<0.01). Norethindrone caused significant weight gain (resolving after cessation) and heavier withdrawal bleeding, but patient satisfaction was higher (80% willing to choose again) and time to conceive was shorter. Norethindrone is ideal for women who need to avoid any breakthrough bleeding, maintain fertility, or present late in their cycle.

Fig. 1 Randomized control Study design and patient inclusion. (Dean J, et al., 2019)

References

Dean J, et al. Norethindrone is superior to combined oral contraceptive pills in short-term delay of menses and onset of breakthrough bleeding: a randomized trial. BMC Womens Health. 2019;19(1):70.

Does Norethindrone require protection from light during long-term storage?

Yes, it is photosensitive. Prolonged exposure to light can cause photodegradation and isomerization. Store in light-resistant, tightly sealed containers.

What is the recommended storage temperature for Norethindrone?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can accelerate oxidative degradation of the ethinyl group.

Is Norethindrone hygroscopic, and how does this affect stability?

It exhibits low hygroscopicity. Under high humidity, it may absorb minimal moisture but is chemically stable. Storage in tightly sealed containers is sufficient.

How is the impurity norethindrone 17α-ethynyl-19-nortestosterone related compound monitored?

This process-related impurity is quantified using a validated HPLC method, ensuring it remains below USP/EP limits throughout shelf life.